The blended refrigerant R-134a is a long-term HFC alternative with similar properties to R-12. It has become the new industry-standard refrigerant for automotive air-conditioning and refrigerator/freezer appliances.

R-134a refrigerating performance will suffer at lower temperatures (below -10 degrees F). Some traditional
R-12 applications have used alternatives other than 134a for lower temperatures.
R-134a requires polyolester (POE) lubricants. Traditional mineral oils and alkyl benzenes do not mix with HFC refrigerants, and their use with 134a may cause operation problems or compressor failures.

In addition, automotive A/C systems may use polyalkaline glycols (PAGs), which are typically not seen in stationary equipment. Both POEs and PAGs will absorb moisture and hold onto it to a much greater extent than traditional lubricants.

The moisture will promote reactions in the lubricant as well as the usual problems associated with water corrosion and acid formation. The best way to dry a wet HFC system is to rely on the filter dryer. Deep vacuum will remove “free” water but not the water that has absorbed into the lubricant.

Appliances, both commercial and self-contained refrigeration, centrifugal chillers, and automotive air conditioning utilize R-134a. Retrofitting equipment with a substitute for R-12 is sometimes difficult; there are a number of considerations to be examined before undertaking the task:

1. For centrifugal compressors it is recommended that the manufacturer’s engineering staff become involved in the project—special parts or procedures may be required. This will ensure proper capacity and reliable operation after the retrofit.

2. Most older direct expansion systems can be retrofitted to R-401A, R-409A, R-414B, or R-416A (R 500 to R-401B or R-409A), so long as there are no components that will cause fractionation within the system to occur.

3. Filter driers should be changed at the time of conversion.

4. The system should be properly labeled with refrigerant and lubricant type.

R-12 Medium/High Temperature Refrigeration  (OF evap)
1. See Recommendation Table (this can be found on the National Refrigerants Web site—click on Technical Manual) for blends that work better in high ambient-heat conditions.

2. Review the properties of the new refrigerant you will use and compare them to R-12. Prepare for any adjustments to system components based on pressure difference or temperature glide.

3. Filter dryers should be changed at the time of conversion.

4. The system should be properly labeled with refrigerant and lubricant type. R-12 Low Temperature Refrigeration (20F evap)

1. See Recommendation Table for blends that have better low-temperature capacity.

2. Review the properties of the new refrigerant you will use and compare them to R-12. Prepare for any adjustments to system components based on pressure difference or temperature glide.

3. Filter dryers should be changed at the time of conversion.

4. The system should be properly labeled with refrigerant and lubricant type. Another blended refrigerant that can be used to substitute for R-12 is 401A . It is a blend of R-22, 152a, and 124. The pressure and system capacity match R-12 when the blend is running an average evaporator temperature of 10 to 20 degrees F. Applications for this refrigerant are as a direct expansion refrigerate for R-12 in air-conditioning systems and in R-500 systems.


How Gas Furnace Operation Works?

The gas furnace is the simplest to operate and understand. Therefore, we will use it here to look at a typical heating system. This type of natural-gas furnace is used to heat millions of homes in the United States.

Figure below shows a simple circuit needed to control a furnace with a blower.

Simple one-stage furnace control system.

Note the location of the blower switch and the limit switch. The transformer provides low voltage for control of the gas solenoid. If the limit switch opens (it is shown in a closed position), there is no power to the transformer and the gas solenoid cannot energize.

This is a safety precaution, because the limit switch will open if the furnace gets too hot. When the thermostat closes, it provides 24 volts to the gas solenoid, which energizes and turns on the gas.

The gas is ignited by the pilot light and provides heat to the plenum of the furnace. When the air in the plenum reaches 120 degrees F, the fan switch closes and the fan starts. The fan switch provides the necessary 120 volts to the fan motor for it to operate.

Once the room has heated up to the desired thermostat setting, the thermostat opens. When it opens, the gas solenoid is de-energized, and the spring action of the solenoid causes it to close off the gas supply, thereby turning off the source of heat.

When the plenum on top of the furnace reaches 90 degrees F, the blower switch opens and turns off the blower. As the room cools down, causing the thermostat to once again close, the cycle starts over again.

The gas solenoid opens to let in the gas, and the pilot light ignites it. The heat causes the temperature to rise in the plenum above the limit switch’s setting, and the switch closes to start the blower.

Once the thermostat setting has been reached, it opens and causes the gas solenoid to turn off the gas supply. The blower continues to run until the temperature in the plenum reaches 90 degrees F, and it turns off the blower by opening.

This cycle is repeated over and over again to keep the room or house at a desired temperature.


How To Handle Refrigerants Safely?

One of the requirements of an ideal refrigerant is that it must be nontoxic. In reality, however, all gases (with the exception of pure air) are more or less toxic or asphyxiating. It is therefore important that wherever gases or highly volatile liquids are used, adequate ventilation be provided, because even nontoxic gases in air produce a suffocating effect.

Vaporized refrigerants (especially ammonia and sulfur dioxide) bring about irritation and congestion of the lungs and bronchial organs, accompanied by violent coughing, vomiting, and, when breathed in sufficient quantity, suffocation. It is of the utmost importance, therefore, that the serviceman subjected to a refrigerant gas find access to fresh air at frequent intervals to clear his lungs.

When engaged in the repair of ammonia and sulfur dioxide machines, approved gas masks and goggles should be used. Carrene, Freon (R-12), and carbon dioxide fumes are not irritating and can be inhaled in considerable concentrations for short periods without serious consequences.

It should be remembered that liquid refrigerant would refrigerate or remove heat from anything it meets when released from a container. In the case of contact with refrigerant, the affected or injured area should be treated as if it has been frozen or frostbitten.

Refrigerant cylinders should be stored in a dry, sheltered, and well-ventilated area. The cylinders should be placed in a horizontal position, if possible, and held by blocks or saddles to prevent rolling. It is of utmost importance to handle refrigerant cylinders with care and to observe the following precautions:

• Never drop the cylinders or permit them to strike each other violently
• Never use a lifting magnet or a sling (rope or chain) when handling cylinders; a crane may be used when a safe cradle or platform is provided to hold the cylinders
• Caps provided for valve protection should be kept on the cylinders at all times except when the cylinders are actually in use
• Never overfill the cylinders; whenever refrigerant is discharged from or into a cylinder, weigh the cylinder and record the weight of the refrigerant remaining in it
• Never mix gases in a cylinder
• Never use cylinders for rollers, supports, or for any purpose other than to carry gas
• Never tamper with the safety devices in valves or on the cylinders
• Open the cylinder valves slowly; never use wrenches or tools except those provided or approved by the gas manufacturer
• Make sure that the threads on regulators or other unions are the same as those on the cylinder-valve outlets.; never force a connection that does not fit
• Regulators and gauges provided for use with one gas must not be used on cylinders containing a different gas
• Never attempt to repair or alter the cylinders or valves
• Never store the cylinders near highly flammable substances (such as oil, gasoline, or waste)
• Cylinders should not be exposed to continuous dampness, salt water, or salt spray
• Store full and empty cylinders apart to avoid confusion
• Protect the cylinders from any object that will produce a cut or other abrasion on the surface of the metal


Q. Does the ultra violet (UV) scanner light work better than an electronic leak detector?
A. No one detection system is better for all situations. But, with a UV lamp you can scan a system more quickly and moving air is never a problem. Solutions also leave a telltale mark at every leak site. Multiple leaks are found more quickly. (See Figure A4.3).

Q. How effective are new light emitting diode (LED) type UV lights?
A. LEDs are small, compact lights for use in close range. Most effective at 6-in. range. The model with two blue UV and three UV bulbs has a slightly greater range. Higher power Yellow Jacket lights are available.

Q. Can LED bulbs be replaced?
A. No. The average life is 110,000 hours.

Q Are RediBeam lamps as effective as the System II lamps?
A. The RediBeam lamp has slightly less power to provide lightweight portability. But with the patented reflector and filter technologies, the RediBeam 100-W bulb produces sufficient UV light for pinpointing leaks.

Q. Does the solution mix completely in the system?
A. Solutions are combinations of compatible refrigeration oil and fluorescent material designed to mix completely with the oil type in the system.

Q. How are solutions different?
A. Solutions are available with mineral, alkylbenzene, PAG, or polyol ester base stock to match oil in the system.

Q. What is universal solution?
A. It is made from polyol ester and mixes well with newer oils. It also works in mineral oil systems, but can be harder to see.

Q. What is the lowest operating temperature?
A. It is -40 degrees F for all solutions. Alkylbenzene in alkylbenzene systems to -100 degrees F.

Q. Does solution stay in the system?
A. Yes. When future leaks develop, just scan for the sources. In over six years of testing, the fluorescent color retained contrast. When the oil is changed in the system, scanner solution must be added to the new oil.

Q. Is the solution safe?
A. Solutions were tested for three years before introduction and have been performance proven in the field since 1989. Results have shown the solutions safe for technicians, the environment and all equipment when used as directed. Solutions are pure and do not contain lead, chromium, or chlorofluorocarbon (CFC) products. Presently, solutions are approved and used by major manufacturers of compressors, refrigerant, and equipment.

Q. How do I determine oil type in a system?
A. Many times the oil is known due to the type of refrigerant or equipment application. Systems should be marked with the kind of oil used. Always tag a system when oil type is changed.

Q. In a system with a mix of mineral and alkylbenzene oil, which scanner solution should be used?
A. Base your choice of solution on whatever oil is present in the larger quantity. If you do not know which oil is in greater quantity, assume it to be alkylbenzene.

Q. How do I add solution to the system?
A. In addition to adding solution using injectors or mist infuser, you have other possibilities. If you do not want to add more gas to the system, connect the injector between the high and low side allowing system pressure to do the job. Or, remove some oil from the system, then add solution to the oil and pump back in.

Q. How is the solution different from visible colored dyes?
A. Unlike colored dyes, Yellow Jacket fluorescent solutions mix completely with refrigerant and oil and do not settle out. Lubrication, cooling capacity, and unit life are not affected; and there is no threat to valves or plugging of filters. The solutions will also work in a system containing dytel.

Q. How do I test the system?
A. Put solution into a running system to be mixed with oil and carried throughout the system. Nitrogen charging for test purposes will not work since nitrogen will not carry the oil. To confirm solution in the system, shine the lamp into the system’s sight glass. Another way is to connect a hose and a sight glass between the high and low sides, and monitor flow with the lamp. The most common reason for inadequate fluorescence is insufficient solution in the system.

Q. Can you tell me more about bulbs?
A. 115-V systems are sold with self-ballasted bulbs in the 150-W range. Bulbs operate in the 365 nanometer long range UV area and produce the light necessary to activate the fluorescing material in the solution. A filter on the front of the lamp allows only “B” band rays to come through. “B” band rays are not harmful.

Q. What is the most effective way to perform an acid test?
A. Scanner solution affects the color of the oil slightly. Use a two-step acid-test kit which factors out the solution in the oil, giving a reliable result.

Q. Can fluorescent product be used in nonrefrigerant applications?
A. Yes, in many applications.


1. Inspect entire A/C system for signs of oil leakage, corrosion cracks, or other damage. Follow the system in a continuous path so no potential leaks are missed.

2. Make sure there is enough refrigerant in a system (about 15 percent of system capacity or 50 psi/min) to generate pressure to detect leaks.

3. Check all service access port fittings. Check seals in caps.

4. Move detector probe at 1 inch/s within inch of suspected leak area.

5. Refrigerant is heavier than air, so position probe below test point.

6. Minimize air movement in area to make it easier to pinpoint the leak.

7. Verify an apparent leak by blowing air into the suspected leak.

8. When checking for evaporator leaks, check for gas in condensate drain tube.

9. Use heated sensor type detector for difficult-to-detect R-134a, R-410A, R-407C, and R-404A.

NEW COMBUSTIBLE GAS DETECTOR (with ultrasensitive, long life sensor)
• Hand-held precision equipment detects all hydrocarbon and other combustible gases including propane, methane, butane, industrial solvents, and more.

• Sensitivity, bar graph, and beeping to signal how much and how close.

• Unit is preset at normal sensitivity, but you can switch to high or low. After warm-up you will hear a slow beeping. Frequency increases when a leak is detected until an alarm sounds when moving into high gas concentration. The illuminated bar graph indicates leak size.

• If no leak is detected in an area you suspect, select high sensitivity. This will detect even low levels in the area to confirm your suspicions. Use low sensitivity as you move the tip over more defined areas, and you will be alerted when the tip encounters the concentration at the leak source.

• Ultrasensitive sensor detects less than 5 ppm methane and better than 2 ppm for propane. It performs equally well on a complete list of detectable gases including acetylene, butane, and isobutane.

• Automatic calibration and zeroing.

• Long-life sensor easily replaced after full service life.

• Gas lines/pipes
• Propane filling stations
• Gas heaters
• Combustion appliances
• Hydrocarbon refrigerant
• Heat exchangers
• Marine bilges
• Manholes
• Air quality
• Arson residue (accelerants)


Window air conditioners (air-cooled room conditioners) and through-the-wall room air conditioners with supplemental heating are designed to cool or heat individual room spaces. Window units are used where low initial cost, quick installation, and other operating or performance criteria outweigh the advantages of more sophisticated systems.

Room units are also available in through-the wall sleeve mountings. Sleeve-installed units are popular in low cost apartments, motels, and homes. Ventilation can be through operable windows or limited outside air ventilation introduced through the self-contained room HVAC unit.

Window units may be used as auxiliaries to a central heating or cooling system or to condition selected spaces when the central system is shut down. These units usually serve only part of the spaces conditioned by the basic system. Both the basic system and window units should be sized to cool the space adequately without the other operating.

A through-the-wall air-cooled room air conditioner is designed to cool or heat individual room spaces. Design and manufacturing parameters vary widely. Specifications range from appliance grade through heavy duty commercial grade, the latter known as packaged terminal air conditioners (PTACs) or packaged terminal heat pumps (PTHPs) (ARI Standard 310/380). With proper maintenance, manufacturers project an equipment life of 10 to 15 years for these units.

Air-cooled heat pumps located on roofs or adjacent to buildings are another type of package equipment with most of the features noted here, with the additional benefit of supply air distribution and equipment outside the occupied space.

This improved ductwork arrangement makes equipment accessible for servicing out the occupied space, unlike in-room units.

• Installation of in-room unit is simple. It usually only requires an opening in the wall or displacement of a window to mount the unit, and connection to electrical power.

• Installation of outside heat pumps is simple with rigging onto concrete pad at grade level or on the roof.

• Generally, the system is well-suited to spaces requiring many zones of individual temperature control.
• Designers can specify electric, hydronic, or steam heat or use an
air-to-air heat pump design.

• Service of in-room equipment can be quickly restored by replacing a defective chassis.

• Equipment life may be less than for large central equipment, typically10 to 15 years, and units are built to appliance standards, rather than building equipment standards.

• Energy use may be relatively high.

• Direct access to outside air is needed for condenser heat rejection; thus, these units cannot be used for interior rooms.

• The louver and wall box must stop wind-driven rain from collecting in the wall box and leaking into the building.

• The wall box should drain to the outside, which may cause dripping on walls, balconies, or sidewalks.

• Temperature control is usually two-position, which causes swings in room temperature.

• Ventilation and economy cycle capabilities are fixed by equipment design.

• Humidification, when required, must be provided by separate equipment.

• Noise and vibration levels vary considerably and are not generally suitable for sound-critical applications.

• Routine maintenance is required to maintain capacity. Condenser and cooling coils must be cleaned, and filters must be changed regularly.


The water-side economizer is another option for reducing energy use. ASHRAE Standard 90.1 addresses its application, as do some state energy codes.

The water-side economizer consists of a water coil in a self contained unit upstream of the direct-expansion cooling coil. All economizer control valves, piping between economizer coil and condenser, and economizer control wiring can be factory installed.

The water-side economizer uses the low cooling tower or evaporative condenser water temperature to either (1) precool entering air, (2) assist mechanical cooling, or (3) provide total system cooling if the cooling water is cold enough. If the economizer is unable to maintain the air-handling unit’s supply air or zone set point, factory mounted controls integrate economizer and compressor operation to meet cooling requirements.

For constant condenser water flow control using a economizer energy recovery coil and the unit condenser, two control valves are factory-wired for complementary control, with one valve driven open while the other is driven closed. This keeps water flow through the condenser relatively constant. In variableflow control, condenser water flow varies during unit operation.

The valve in bypass/energy recovery loop is an on/off valve and is closed when the economizer is enabled. Water flow through the economizer coil is modulated by its automatic control valve, allowing variable cooling water flow as cooling load increases (valve opens) and reduced flow on a decrease in cooling demand.

If the economizer is unable to satisfy the cooling requirements, factory-mounted controls integrate economizer and compressor operation. In this operating mode, the economizer valve is fully open. When the self-contained unit is not in cooling mode, both valves are closed. Reducing or eliminating cooling water flow reduces pumping energy.


• Compressor energy is reduced by precooling entering air. Often, building load can be completely satisfied with an entering condenser water temperature of less than 55°F. Because the wet-bulb temperature is always less than or equal to the dry-bulb temperature, a lower discharge air temperature is often available.

• Building humidification does not affect indoor humidity by introducing outside air.

• No external wall penetration is required for exhaust or outside air ducts.

• Controls are less complex than for air-side economizers, because they are often inside the packaged unit.

• The coil can be mechanically cleaned.

• More net usable floor area is available because large outside and relief air ducts are unnecessary.


• Cooling tower water treatment cost is greater.

• Air-side pressure drop may increase with the constant added resistance of a economizer coil in the air stream.

• Condenser water pump pressure may increase slightly.

• The cooling tower must be designed for winter operation.

• The increased operation (including in winter) required of the cooling tower may reduce its life.


With some decentralized systems, an air-side economizer is an option, if not an energy code requirement (check state code for criteria). The air-side economizer uses cool outside air to either assist mechanical cooling or, if the outside air is cool enough, provide total cooling.

It requires a mixing box designed to allow 100% of the supply air to be drawn from outside. It can be a field-installed accessory that includes an outside air damper, relief damper, return air damper, filter, actuator, and linkage.

Controls are usually a factory-installed option. Self-contained units usually do not include return air fans. A barometric relief, fan-powered relief fan, or return/exhaust fan may be provided as an air-side economizer.

The relief fan is off and discharge/ exhaust dampers are closed when the air-side economizer is inactive.


• Substantially reduces compressor, cooling tower, and condenser water pump energy requirements, generally saving more energy than a water-side economizer.

• Has a lower air-side pressure drop than a water-side economizer.

• Reduces tower makeup water and related water treatment.

• May improve indoor air quality by providing large amounts of outside air during mild weather.


• In systems with larger return air static pressure requirements, return or exhaust fans are needed to properly exhaust building air and take in outside air.

• If the unit’s leaving air temperature is also reset up during the airside economizer cycle, humidity control problems may occur and the fan may use more energy.

• Humidification may be required during winter.

• More and/or larger air intake louvers, ducts, or shafts may be required.


Piping should deliver refrigerant, heating water, chilled water, condenser water, fuel oil, gas, steam, and condensate drainage and return to and from HVAC equipment as directly, quietly, and economically as possible.

Structural features of the building generally require mechanical and electrical coordination to accommodate P-traps, pipe pitch-draining of low points in the system, and venting of high points.

When assessing application of pipe distribution to air distribution, the floor-to-floor height requirement can influence the pipe system: it requires less ceiling space to install pipe.

An alternative to horizontal piping is vertical pipe distribution, which may further reduce floor-to-floor height criteria.

Pipe Systems
HVAC piping systems can be divided into two parts: (1) piping in the central plant equipment room and (2) piping required to deliver refrigerant, heating water, chilled water, condenser water, fuel oil, gas, steam, and condensate drainage and return to and from decentralized HVAC and process equipment throughout the building.

Pipe Insulation
In new construction and renovation projects, certain HVAC piping may or may not be insulated depending on code requirements.

ASHRAE Standard 90.1 and Chapter 26 of the 2005 ASHRAE Handbook Fundamentals have information on insulation and calculation methods.



In 1987 the Montreal Protocol, an international environmental agreement, established requirements that began the worldwide phaseout of ozone-depleting chlorofluorocarbons. These requirements were later modified, leading to the phaseout, in 1996, of CFC production in all developed nations.

In 1992 an amendment to the Montreal Protocol established a schedule for the phaseout of HCFCs (hydrochlorofluorocarbons). HCFCs are substantially less damaging to the ozone layer than CFCs.

However, they still contain ozonedestroying chlorine. The Montreal Protocol, as amended, is carried out in the U.S. through Title VI of the Clean Air Act. This act is implemented by the Environmental Protection Agency.

An HCFC known as R-22 has been the refrigerant of choice for residential heat-pump and air-conditioning systems for more than four decades. Unfortunately for the environment, release of R-22 resulting from system leaks contributes to ozone depletion. In addition, the manufacture of R-22 results in a byproduct that contributes significantly to global warming.

As the manufacture of R-22 is phased out over the coming years as part of the agreement to end production of HCFCs, manufacturers of residential air-conditioning systems are beginning to offer equipment that uses ozone-friendly refrigerants.

Many homeowners may be misinformed about how much longer R-22 will be available to service their central A/C systems and heat pumps. The EPA document assists consumers in deciding what to consider when purchasing a new A/C system or heat pump or repairing an existing system.

Under the terms of the Montreal Protocol, the U. S. agreed to meet certain obligations by specific dates. These will affect the residential heat-pump and air -conditioning industry.

In accordance with the terms of the protocol, the amount of all HCFCs that can be produced nationwide was to be reduced by 35 percent by January 1, 2004. In order to achieve this goal, the U.S. ceased production of HCFC-141b, the most ozone-damaging of this class of chemicals, on January 1, 2003.

This production ban should greatly reduce nationwide use of HCFCs as a group and make it likely that the 2004 deadline will have a minimal effect on R-22 supplies.

After January 1, 2010, chemical manufacturers may still produce R-22 to service existing equipment but not for use in new equipment. As a result, heating, ventilation and air-conditioning (HVAC) manufacturers will only be able to use preexisting supplies of R-22 in the production of new air conditioners and heat pumps.

These existing supplies will include R-22 recovered from existing equipment and recycled by licensed reclaimers. Use of existing refrigerant, including refrigerant that has been recovered and recycled, will be allowed beyond January 1, 2020 to service existing systems. However, chemical manufacturers will no longer be able to produce R-22 to service existing air conditioners and heat pumps.



Several regulations have been issued under Section 608 of the Clean Air Act to govern the recycling of refrigerants in stationary systems and to end the practice of venting refrigerants to the air. These regulations also govern the handling of halon fire-extinguishing agents.

A Web site and both the regulations themselves and fact sheets are available from the EPA Stratospheric Ozone Hotline at 1-800-296-1996. The handling and recycling of refrigerants used in motor-vehicle air conditioning systems is governed under section 609 of the Clean Air Act.

In 2005 EPA finalized a rule amending the definition of refrigerant to make certain that it only includes substitutes that consist of a class I or class II ozone-depleting substance (ODS). This rule also amended the venting prohibition to make certain that it remains illegal to knowingly vent non exempt substitutes that do not consist of a class I or class II ODS, such as R-134a and R-410A.

In the same year EPA published a final rule extending the required leak-repair practices and the associated reporting and record-keeping requirements to owners and/or operators of comfort-cooling, commercial- refrigeration, or industrial-process refrigeration appliances containing more than 50 pounds of a substitute refrigerant if the substitute contains a class I or class II ozone-depleting substance (ODS).

In addition, EPA defined leak rate in terms of the percentage of the appliance’s full charge that would be lost over a consecutive 12-month period if the current rate of loss were to continue over that period. EPA now requires calculation of the leak rate whenever a refrigerant is added to an appliance.

In 2004 EPA finalized a rule sustaining the Clean Air Act prohibition against venting hydrofluorocarbon (HFC) and perfluorocarbon (PFC) refrigerants. This rule makes the knowing venting of HFC and PFC refrigerants during the maintenance, service, repair, and disposal of air-conditioning and refrigeration equipment (i.e., appliances) illegal under Section 608 of the Clean Air Act.

The ruling also restricts the sale of HFC refrigerants that consist of an ozone-depleting substance (ODS) to EPA-certified technicians. However, HFC refrigerants and HFC refrigerant blends that do not consist of an ODS are not covered under “The Refrigerant Sales Restriction,” a brochure that documents the environmental and financial reasons to replace CFC chillers with new, energy-efficient equipment.

A partnership of governments, manufacturers, NGOs (nongovernmental organizations), and others have endorsed the brochure to eliminate uncertainty and underscore the wisdom of replacing CFC chillers.


Moisture should be kept out of refrigeration systems, since it can corrode parts of the system. Whenever low temperatures are produced, the water or moisture can freeze.

If freezing of the metering device occurs, then refrigerant flow is restricted or cut off. The system will have a low efficiency or none at all. The degree of efficiency will depend upon the amount of icing or the part affected by the frozen moisture.

All refrigerants will absorb water to some degree. Those that absorb very little water permit free water to collect and freeze at low-temperature points.

Those that absorb a high amount of moisture will form corrosive acids and corrode the system. Some systems will allow water to be absorbed and frozen. This causes corrosion.

Hydrolysis is the reaction of a material, such as Freon 12 or methyl chloride, with water. Acid materials are formed. The hydrolysis rate for the Freon compounds as a group is low compared with other halogenated compounds.

Within the Freon group, however, there is considerable variation. Temperature, pressure, and the presence of other materials also greatly affect the rate. Typical hydrolysis rates for the Freon compounds and other halogenated compounds are given in Table below.

Hydrolysis rate in water grams/litre of water/year.

With water alone at atmospheric pressure, the rate is too low to be determined by the analytical method used. When catalyzed by the presence of steel, the hydrolysis rates are detectable but still quite low. At saturation pressures and a higher temperature, the rates are further increased.

Under neutral or acidic conditions, the presence of hydrogen in the molecule has little effect on the hydrolytic stability. However, under alkaline conditions compounds containing hydrogen, such as Freon 22 and Freon 21, tend to be hydrolyzed more rapidly.


A brief summary of the effect of Freon compounds on various plastic materials follows. However, compatibility should be tested for specific applications. Differences in polymer structure and molecular weight, plasticizers, temperature, and pressure may alter the resistance of the plastic toward the Freon compound:

• Teflo-TFE-fluorocarbon: no swelling observed when submerged in Freon liquids, but some diffusion found with Freon 12 and Freon 22

• Polychlorotriflororoethylene: slight swelling, but generally suitable for use with Freon compounds

• Polyvinyl alcohol: not affected by the Freon compounds but very sensitive to water; used especially in tubing with an outer protective coating

• Vinyl: resistance to the Freon compounds depends on vinyl type and plasticizer, and considerable variation is found; samples should be tested before use

• Orlon-acrylic fiber: generally suitable for use with the Freon compounds

• Nylon: generally suitable for use with Freon compounds but may tend to become brittle at
high temperatures in the presence of air or water; tests at 250 degrees F (121 degrees C) with Freon 12 and Freon 22 showed the presence of water or alcohol to be undesirable, so adequate testing should be carried out

• Polyethylene: may be suitable for some applications at room temperatures; however, it should be thoroughly tested since greatly different results have been found with different samples

• Lucite®-acrylic resin (methacrylate polymers): dissolved by Freon 22 but generally suitable for use with Freon 12 and Freon 114 for short exposure; with long exposure it tends to crack,
 craze, and become cloudy; use with Freon 113 and Freon 11 may be questionable

• Cast Lucite acrylic resin: much more resistant to the effect of solvents than extruded resin; can
probably be used with most of the Freon compounds

• Polystyrene: Considerable variation found in individual samples but generally not suited for use with Freon  compounds; some applications might be acceptable with Freon 114

• Phenolic resins: usually not affected by Freon compounds but composition of resins of this type may be quite different; samples should be tested before use

• Epoxy resins: resistant to most solvents and entirely suitable for use with the Freon compounds

• Cellulose acetate or nitrate: suitable for use with Freon compounds

• Delrin-acetal resin: suitable for use with Freon compounds under most conditions

• Elastomers: considerable variation is found in the effect of Freon compounds, depending on the particular compound and elastomer type, but in nearly all cases a satisfactory combination can be found; in some instances the presence of other materials, such as oils, may give unexpected results, so preliminary testing of the system involved is recommended


Most of the commonly used construction metals, such as steel, cast iron, brass, copper, tin, lead, and aluminum, can be used satisfactorily with Freon compounds under normal conditions of use. At high temperatures some of the metals may act as catalysts for the breakdown of the compound.

The tendency of metals to promote thermal decomposition of Freon compounds is in the following general order, with those metals that least promote thermal decomposition listed first:

Stainless steel
1340 steel

The above order is only approximate. Exceptions may be found with individual Freon compounds or for special conditions of use.

Magnesium alloys and aluminum containing more than 2 percent magnesium are not recommended for use in systems containing Freon compounds if water may be present. Zinc is not recommended for use with Freon 113.

Experience with zinc and other Freon compounds has been limited, and no unusual reactivity has been observed. However, it is more chemically reactive than other common construction metals, so it would seem wise to avoid its use with the Freon compounds unless adequate testing is carried out.

Some metals may be questionable for use in applications requiring contact with Freon compounds for long periods of time or unusual conditions of exposure. These metals, however, can be cleaned safely with Freon solvents.

Cleaning applications are usually for short exposures at moderate temperatures. Most halocarbons may react violently with highly reactive materials, such as sodium, potassium, and barium in their free metallic form.

Materials become more reactive when finely ground or powdered. In this state, magnesium and aluminum may react with fluorocarbons, especially at higher temperatures.

Highly reactive materials should not be brought into contact with fluorocarbons until a careful study is made and appropriate safety precautions are taken.


If the space served by a conditioning unit operates on a regular schedule, a timeclock or setback thermostat is usually the best method of automatically starting and stopping conditioning. For greater control flexibility, you can combine timeclocks and setback thermostats with controls that respond to other conditions, such as outdoor temperature, occupancy, etc.

Timeclocks and setback thermostats are not appropriate for spaces that operate on irregular schedules, such as conference rooms, auditoriums, and surgical suites. Unfortunately, facility managers sometimes try to schedule specific times for conditioning such spaces, most commonly through an energ management system.

This inevitably leads to dissatisfaction.

Don’t use temperature setback if the thermostatic control system would use energy to force the setback temperature. This limitation exists in units that provide both heating and cooling, where neither can be turned off.

For example, four-pipe fan-coil units with pneumatic controls are sometimes installed with a single thermostatic element controlling both the heating and cooling coils. These are installed in some luxury hotels so that guests do not have to select heating or cooling.

If a setback thermostat were used with this type of system, switching to the lower nighttime temperature would consume energy to cool the space to the nighttime temperature, and to maintain that temperature until the setback thermostat switched back to the daytime temperature.

If the conditioning unit uses reheat, study the unit’s controls before using temperature setback. Setback while reheating actually increases energy consumption.  (Reheat is rarely used in room conditioning units. When it is used, the purpose is usually to control humidity.

To minimize energy consumption for dehumidification, the reheat should be controlled by a humidistat in the space.)

Comparison of Timeclocks and Setback Thermostats
In most cases, but not in all, a setback thermostat is preferable to a timeclock. Setback thermostats behave in the same way as timeclocks, until the temperature falls (or rises) to the temperature limit that is set. The main advantage of a setback thermostat is that it restarts the conditioning unit if the temperature drops to the lower setting.

This feature keeps the space warm enough for a quick warm-up, or you can use a setback thermostat
as a safety feature to protect against excessively low (or high) temperature.

If the conditioning unit has a continuously running fan, using a timeclock to control the power to the unit saves fan energy, whereas a setback thermostat allows the fan to keep running. In some cases, it is fairly easy to install a setback thermostat so that it controls the operation of the entire unit.

Setback thermostats cost more than timeclocks, but the labor cost of installing a setback thermostat in the thermostat circuit usually is less than the cost of installing a timeclock in the main power circuit. On the other hand, you could install a timeclock in the thermostat circuit.


A Guide On How To Choose The Appropriate Air Conditioning System?

Each of the four general types of air-conditioning systems has numerous variations, so choosing a system is not a simple task. With experience, it becomes easier. However, a new client, a new type of building or a very different climate can be a challenge.

We are now going to briefly outline the range of factors that affect system choice and finish by introducing a process that designers can use to help choose a system.

The factors, or parameters that influence system choice can conveniently be divided into the following groups:

Building design
Location issues
Utilities: availability and cost
Indoor requirements and loads
  Client issues

Building Design
The design of the building has a major influence on system choice. For example, if there is very little space for running ducts around the building, an all-air system may not fit in the available space.

Location Issues
The building location determines the weather conditions that will affect the building and its occupants. For the specific location we will need to consider factors like:

site conditions
peak summer cooling conditions
summer humidity
peak winter heating conditions
wind speeds
sunshine hours
typical snow accumulation depths

The building location and, at times, the client, will determine what national, local, and facility specific codes must be followed. Typically, the designer must follow the local codes. These include:

a. Building code that includes a section on HVAC design including ventilation.
b. Fire code that specifies how the system must be designed to minimize the start and spread of fire and smoke.
c. Energy code that mandates minimum energy efficiencies for the building and components. We will be considering the ASHRAE Standard 90.1 2004
d. Energy Standard for Buildings Except Low-Rise Residential Buildings7 and other energy conservation issues
In addition, some types of buildings, such as medical facilities, are designed to consensus codes which may not be required by local authorities but which may be mandated by the client. An example is The American Institute of Architects Guidelines for Design and Construction of Hospital and Health Care Facilities, which has guidelines that are extremely onerous in some climates.

Utilities: Availability and Cost
The choice of system can be heavily influenced by available utilities and their costs to supply and use. So, if chilled water is available from the adjacent building, it would probably be cost advantageous to use it, rather than install new unitary refrigerant-based units in the new building.

Then again, the cost of electricity may be very high at peak periods, encouraging the design of an electrically efficient system with low peak-demand for electricity. We will be introducing some of the ways to limit the cost of peaktime electricity in our final chapter.

The issues around electrical pricing and usage have become very well publicized in North America over recent years. The ASHRAE course Fundamentals of Electrical Systems and Building Electrical Energy Use introduces this topic.

Indoor Requirements and Loads
The location effects and indoor requirements provide all the necessary information for load calculation for the systems. 

The thermal and moisture loads – Occupants’ requirements and heat output from lighting and equipment affect the demands on the air-conditioning system.

Outside ventilation air – The occupants and other polluting sources, such as cooking, will determine the requirements.

Zoning – The indoor arrangement of spaces and uses will determine if, and how, the system is to be zoned.

Other indoor restrictions may be very project, or even zone specific. For example, a sound recording studio requires an extremely quiet system and negligible vibration. The methods of calculating the heating and cooling loads are fully explained, with examples, in the ASHRAE course Fundamentals of Heating and Cooling Loads.

Client Issues
Buildings cost money to construct and to use. Therefore, the designer has to consider the clients’ requirements both for construction and for in-use costs. For example, the available construction finances may dictate a very simple system.

Alternatively, the client may wish to finance a very sophisticated, and more expensive system to achieve superior performance, or to reduce in-use costs. In addition to cost structures, the availability of maintenance staff must be considered.

A building at a very remote site should have simple, reliable systems, unless very competent and well supported maintenance staff will be available. Clients’ approvals may be gained, or lost, based on their own previous experience with other projects or systems. Therefore, it is important for the designer to find out, in advance, if the client has existing preconceptions about potential systems.

System Choice
While all the above factors are considered when choosing a system, the first step in making a choice is to calculate the system loads and establish the number and size of the zones. Understanding of the loads may eliminate some systems from consideration. 

For example:  In warm climates where heating is not required only systems providing cooling need be considered. If there are significant variations in operating hours between zones, a system which cannot be shut down on a zone-by-zone basis may not be worth considering.

Typically, after some systems have been eliminated for specific reasons, one needs to do a point-by-point comparison to make a final choice. This is where the system-choice matrix is a very useful tool.


Air-and-water Systems
Another group of systems, air-and-water systems, provide all the primary ventilation air from a central system, but local units provide additional conditioning. The primary ventilation system also provides most, or all, of the humidity control by conditioning the ventilation air.

The local units are usually supplied with hot or chilled water. These systems are particularly effective in perimeter spaces, where high heating and cooling loads occur.

Although they may use electric coils instead of water, they are grouped under the title “air-and-water systems.”

For example, in cold climates substantial heating is often required at the perimeter walls. In this situation, a hot-water-heating system can be installed around the perimeter of the building while a central air system provides cooling and ventilation.

All-water Systems
When the ventilation is provided through natural ventilation, by opening windows, or other means, there is no need to duct ventilation air to the zones from a central plant. This allows all processes other than ventilation to be provided by local equipment supplied with hot and chilled water from a central plant.

These systems are grouped under the name “all-water systems.”

The largest group of all-water systems are heating systems. The detailed design of these heating systems is covered in the ASHRAE course Fundamentals of Heating Systems.

Both the air-and-water and all-water systems rely on a central supply of hot water for heating and chilled water for cooling. The detailed designs and calculations for these systems can be found in the ASHRAE course Fundamentals of Water System Design


What Is A Zoned Air Conditioning System?

The air-conditioning system considered so far provides a single source of air with uniform temperature to the entire space, controlled by one space thermostat and one space humidistat. However, in many buildings there is a variety of spaces with different users and varying thermal loads.

These varying loads may be due to different inside uses of the spaces, or due to changes in cooling loads because the sun shines into some spaces and not others. Thus our simple system, which supplies a single source of heating or cooling, must be modified to provide independent, variable cooling or heating to each space.

When a system is designed to provide independent control in different spaces, each space is called a “zone.”

A zone may be a separate room. A zone may also be part of a large space. For example, a theatre stage may be a zone, while the audience seating area is a second zone in the same big space.

Each has a different requirement for heating and cooling. This need for zoning leads us to the four broad categories of air-conditioning systems, and consideration of how each can provide zoned cooling and heating.

The four systems are

1. All-air systems

2. Air-and-water systems

3. All-water systems

4. Unitary, refrigeration-based systems


What Is A Water Hydraulic Turbine?

Turbine is a machine wherein rotary motion is obtained by centrifugal forces, which result from a change in the direction of high velocity fluid jet that issues from a nozzle. Water turbine is a prime mover, which uses water as the working substance to generate power.

A water turbine uses the potential and kinetic energy of water and converts it into usable mechanical energy. The fluid energy is available in the natural or artificial high level water reservoirs, which are created by constructing dams at appropriate places in the flow path of rivers.

When water from the reservoir is taken to the turbine, transfer of energy takes place in the blade passages of the unit. Hydraulic turbines in the form of water wheels have been used since ages; presently their application lies in the field of electric power generation.

The mechanical energy made available at the turbine shaft is used to run an electric generator, which is directly coupled, to the turbine shaft. The power generated by utilizing the potential and kinetic energy of water has the advantages of high efficiency, operational flexibility, low wear tear, and ease of maintenance.

Despite the heavy capital cost involved in constructing dams and reservoirs, in running pipelines and in turbine installation (when compared to an equivalent thermal power plant) different countries have tried to tap all their waterpower resources.

Appropriate types of water turbines have been installed for most efficient utilization.

Hydroelectric power is a significant contributor to the world’s energy sources.

Water (hydraulic) turbines have been broadly classified as,
1. Impulse 2. Reaction


What Are The Different Types Of Energy?

There are various types of energy which, they include nuclear, electrical, thermal, chemical, and radiant energy. In addition, gravitational potential energy and kinetic energy that combines to produce mechanical energy.

Nuclear energy produces heat by fission on nuclei, which is generated by heat engines. Nuclear energy is the world’s largest source of emission-free energy.

There are two processes in Nuclear energy fission and fusion. In fission, the nuclei of uranium or plutonium atoms are split with the release of energy. In fusion, energy is released when small nuclei combine or fuse.

The fission process is used in all present nuclear power plants, because fusion cannot be controlled. Nuclear energy is used to heat steam engines. A Nuclear power plant is a steam engine using uranium as its fuel, and it suffers from low efficiency.

Electricity powers most factories and homes in our world. Some things like flashlights and Game Boys use electricity that is stored in batteries as chemical energy. Other items use electricity that comes from an electrical plug in a wall socket.

Electricity is the conduction or transfer of energy from one place to another. The electricity is the flow of energy. Atoms have electrons circling then, some being loosely attached. When electrons move among the atoms of matter, a current of electricity is created.

Thermal energy is kinetic and potential energy, but it is associated with the random motion of atoms in an object. The kinetic and potential energy associated with this random microscopic motion is called thermal energy.

A great amount of thermal energy (heat) is stored in the world’s oceans. Each day, the oceans absorb enough heat from the sun to equal the energy contained in 250 billion barrels of oil (Ocean Thermal Energy Conversion Systems).

Chemical energy is a form of energy that comes from chemical reactions, in which the chemical reaction is a process of oxidation. Potential energy is released when a chemical reaction occurs, which is called chemical energy.

A car battery is a good example, because the chemical reaction produces voltage and current to start the car. When a plant goes through a process of photosynthesis, what the plant is left with more chemical energy than the water and carbon dioxide. Chemical energy is used in science labs to make medicine and to product power from gas.

Radiant energy exists in a range of wavelengths that extends from radio waves that many be thousands of meters long to gamma rays with wavelengths as short as a million-millionth (10– 12) of a meter. Radiant energy is converted to chemical energy by the process of photosynthesis.

The next two types of energy go hand and hand, gravitational potential energy and kinetic energy. The term energy is motivated by the fact that potential energy and kinetic energy are different aspects of the same thing, mechanical energy.

Potential energy exists whenever an object which has mass has a position within a force field. The potential energy of an object in this case is given by the relation PE = mgh, where PE is energy in joules, m is the mass of the object, g is the gravitational acceleration, and h is the height of the object goes.

Kinetic energy is the energy of motion. An object in motion, whether it be vertical or horizontal motion, has kinetic energy. There are different forms of kinetic energy vibrational, which is the energy due to vibrational motion, rotational, which is the energy due to rotational motion, and transnational, which is the energy due to motion from one location to the other. The equation for kinetic energy is ½ mv2, where m is the mass and v is the velocity. This equation shows that the kinetic energy of an object is directly proportional to the square of its speed.


Energy is the capacity for doing work, generating heat, and emitting light. The equation for work is the force, which is the mass time the gravity times the distance. Heat is the ability to change the temperature of an object or phase of a substance.

For example, heat changes a solid into a liquid or a liquid into a vapor. Heat is part of the definition of energy. Another part of the definition of energy is radiation, which is the light and energy emitted in the form of waves traveling at the speed of light.

Energy is measured in units of calorie, quad, and joule. A kilocalorie is the amount of energy or heat required to raise the temperature of 1 kilogram of water from 14.5°C to 15.5°C. The quad unit is used to measure energy needed for big countries. The final measurement of energy is joules.

Energy is an essential input for economic development and improving quality of life

These renewable, non-commercial sources have been used extensively for hundreds of years but in a primitive and ineffective way. Indiscriminate use of non-commercial energy sources is leading to an energy crisis in the rural areas. Seventh Plan laid emphasis on the development and accelerated utilisation of renewable energy sources in rural and urban areas.

A major Policy of the Government is directed towards increasing the use of coal in household and of electricity in transport sector in order to reduce dependence on oil, which is becoming scarce gradually.

The Government has formulated an energy policy with objectives of ensuring adequate energy supply at minimum cost, achieving self-sufficiency in energy supplies and protecting environment from adverse impact of utilising energy resources in an injudicious manner. Main elements of the policy are:

1. Accelerated exploitation of domestic conventional energy resources-oil, coal, hydro and nuclear power;
2. Intensification of exploration to increase indigenous production of oil and gas;
3. Management of demand for oil and other forms of energy;
4. Energy conservation and management;
5. Optimisation of utilisation of existing capacity in the country;
6. Development and exploitation of renewable sources of energy to meet energy requirements of rural communities;
7. Intensification of research and development activities in new and renewable energy sources; and
8. Organisation of training far personnel engaged at various levels in the energy sector.

Development of conventional forms of energy for meeting the growing energy needs of the society at a reasonable cost is the responsibility of Government viz., Department of Power, Coal and Petroleum and Natural Gas. Development and promotion of non-conventional/alternate/new and renewable sources of energy such as Solar, Wind and Bio-energy, etc., are also getting sustained attention from the Department of Non-Conventional Energy Sources created in September, 1982. Nuclear Energy Development is being geared up by the Department of Atomic Energy to contribute significantly to overall energy availability in the Country.

Energy Conservation is being given the highest-priority and is being used as a tool to bridge the gaps between demand and supply of energy. An autonomous body, namely Energy Management Centre, has been set up on ten April, 1989, as a nodal agency for energy conservation projects.


Chemicals that interfere with the transfer of oxygen to the tissues are called asphyxiants. The exposed individual literally suffocates because the bloodstream cannot supply enough oxygen for life.

There are two main classes of asphyxiants—simple and chemical. Simple asphyxiants displace oxygen in the air, thereby leaving less or none for breathing.

Chemical asphyxiants cause the same effect by interfe ring with the body’s ability to take up, transport, or use oxygen. Simple asphyxiants are a major hazard in confined spaces, where breathable air can be displaced by gas from sewa g e, for instance.

When the normal oxygen level of 21% drops to 16%, breathing and other problems begin, such as lightheadedness, buzzing in the ears, and rapid heartbeat. Simple asphyxiants in construction include argon, propane, and methane.

These chemicals usually have no other toxic properties asphyxiant. It combines with the oxygen-carrying compound in the blood and reduces its ability to pick up “new” oxygen.

Hydrogen sulphide, on the other hand, interferes with the chemical pathways which transfer the oxygen, while hydrogen cyanide paralyzes the respiratory centre of the brain.

Absorption through the skin is another common form of entry for toxic substances (e.g., organic solvents). The skin is the largest organ of the body and has the largest surface area that can come into contact with harmful substances.

Some chemicals can penetrate through the skin, reach the bloodstream, and get to other parts of the body where they can cause harm. Toluene and Cellosolve are examples of chemicals which are absorbed through the skin. Mineral spirits and other solvents used in the manufacturing of paint can easily penetrate the skin.

The skin protects the internal organs of the body from the outside environment. Its outer layer is composed of hardened, dead cells which make the skin resistant to daily wear and tear. Sweat glands cool the body when the environment is hot.

Sebaceous glands produce oils which repel water. A network of small blood vessels, or capillaries, plays a key role in controlling body temperature. These capillaries open when it is hot, radiating heat outward into the air, and constrict when it is cold, conserving heat in the body.

The skin also has a protective layer of oils and proteins which helps to prevent injury or penetration by harmful substances.

A substance may be absorbed and travel to another part of the body, or it may cause damage at the point of entry (the skin), and start the disease process. Such substances are usually identified in an MSDS with a notation “skin” along with their exposure limits, indicating that the exposure can occur through the skin, mucous membranes, or eyes, or may damage the skin itself.


The airways of the respiratory system have developed an elaborate system of defences which trap all but the smallest dust particles. This system consists of hairs in the nose and mucus in the trachea or bronchi.

The mucus is produced continuously by special cells in the walls of the larger airways. It is moved upward and to the back of the throat by the whipping action of cilia—tiny, hair-like projections on the cells of the trachea and bronchi.

Large dust particles are trapped in the mucus and are either swallowed or spit out. Particles smaller than 0.5 microns (1 inch has 25,400 microns) may remain airborne and are exhaled.

The most dangerous size of dust particles is 0.5-7.0 microns. Much too small to be seen with the naked eye, they can evade the defence system and reach the lungs.

Once in the lungs, these tiny particles of dust may cause extensive scarring of the delicate air sacs. This scarring starts the disease process which produces severe shortness of breath.

Most dust particles are too large to pass through the walls of the alveoli, but gases, vapours, mists, and fumes can all enter the bloodstream through the lungs. In addition, welding fumes or truck exhausts can stimulate the lung’s defences to produce large amounts of phlegm, causing the condition known as chronic bronchitis.

These same substances can destroy the delicate air sacs of the lungs, causing emphysema.

Because the lungs are in such intimate contact with so many pollutants in workplace air, they are the prime target for occupational carcinogens.


In addition to the legal responsibilities on management, there are many specifi c responsibilities imposed by each organization’s health and safety policy. The responsibilities cover directors, senior managers, site managers, department managers, supervisors and employees.

Many organizations will not fi t this exact structure but most will have those who direct, those who manage or supervise and those who have no line responsibility but have responsibilities to themselves and fellow workers. Because of the special role and importance of directors, these are covered here in detail.

Directors’ responsibilities
The Chairman of the Health and Safety Commission said at the launch of the guidance on Directors’ responsibilities:

Health and safety is a boardroom issue.

Good health and safety refl ects strong leadership from the top and that is what we want to see. The company whose chairperson or chief executive is the champion of health and safety sends the kind of message which delivers good performance on the ground.

Those who are at the top have a key role to play, which is why boards are being asked to nominate one of their members to be a ‘health and safety’ director. But appointing a health and safety director or department does not absolve the Board from its collective responsibility to lead and oversee health and safety management.

Directors’ Responsibility for Health & Safety INDG 343, sets out the following action points for directors:

➤ the Board needs to accept formally and publicly its collective role in providing health and safety leadership in its organization
➤ each member of the Board needs to accept their individual role in providing health and safety leadership for their organization
➤ the Board needs to ensure that all board decisions reflect its health and safety intentions, as articulated in the health and safety policy statement. It is important for boards to remember that, although health and safety functions can (and should) be delegated, legal responsibility for health and safety rests with the employer
➤ the Board needs to recognize its role in engaging the active participation of workers in improving health and safety
➤ the Board needs to ensure that it is kept informed of, and alert to, relevant health and safety risk management issues. The Health and Safety Commission recommends that boards appoint one of their number to be the ‘Health and Safety Director’.

Directors need to ensure that the Board’s health and safety responsibilities are properly discharged. The Board will need to:

➤ carry out an annual review of health and safety performance
➤ keep the health and safety policy statement up to date with current board priorities and review the policy at least every year
➤ ensure that there are effective management systems for monitoring and reporting on the organization’s health and safety performance
➤ ensure that any signifi cant health and safety failures and their investigation are communicated to board members
➤ ensure that when decisions are made the health and safety implications are fully considered

➤ ensure that regular audits are carried out to check that effective health and safety risk management systems are in place.

By appointing a ‘Health and Safety Director’ there will be a board member who can ensure that these health and safety risk management issues are properly addressed, both by the Board and more widely throughout the organization.

The Chairman and/or Chief Executive have a critical role to play in ensuring risks are properly managed and that the Health and Safety Director has the necessary competence, resources and support of other board members to carry out their functions.

Indeed, some boards may prefer to see all the health and safety functions assigned to their Chairman and/or Chief Executive. As long as there is clarity about the health and safety responsibilities and functions, and the Board properly addresses the issues, this is acceptable.

The health and safety responsibilities of all board members should be clearly articulated in the organization’s statement of health and safety policy and arrangements. It is important that the role of the Health and Safety Director should not detract either from the responsibilities of other directors for specifi c areas of health and safety risk management or from the health and safety responsibilities of the Board as a whole.



The following checklist is intended as an aid to the writing and review of a safety policy. It is derived from the booklet Writing a safety policy statement published by the HSE in booklet HSC 6.

General policy and organization
➤ Does the statement express a commitment to health and safety and are your obligations towards your employees made clear?
➤ Does it say which senior manager is responsible for seeing that it is implemented and for keeping it under review, and how this will be done?
➤ Is it signed and dated by you or a partner or senior director?
➤ Have the views of managers and supervisors, safety representatives and of the safety committee been taken into account?
➤ Were the duties set out in the statement discussed with the people concerned in advance, and accepted by them, and do they understand how their performance is to be assessed and what resources they have at their disposal?
➤ Does the statement make clear that co-operation on the part of all employees is vital to the success of your health and safety policy?
➤ Does it say how employees are to be involved in health and safety matters, for example, by being consulted, by taking part in inspections, and by sitting on a safety committee?
➤ Does it show clearly how the duties for health and safety are allocated and are the responsibilities at different levels described?

➤ Does it say who is responsible for the following matters (including deputies where appropriate)?

– reporting investigations and recording accidents
– fi re precautions, fi re drill, evacuation procedures
– fi rst aid
– safety inspections
– the training programme
– ensuring that legal requirements are met, for example, regular testing of lifts and notifying accidents to the health and safety inspector.

Arrangements that need to be considered
➤ Keeping the workplace, including staircases, floors, ways in and out, washrooms, etc. in a safe and clean condition by cleaning, maintenance and repair
➤ The requirements of the Work at Height

➤ Any suitable and suffi cient risk assessments.

Plant and substances
➤ Maintenance of equipment such as tools, ladders, etc. Are they in a safe condition?
➤ Maintenance and proper use of safety equipment such as helmets, boots, goggles, respirators, etc.
➤ Maintenance and proper use of plant, machinery and guards.
➤ Regular testing and maintenance of lifts, hoists, cranes, pressure systems, boilers and other dangerous machinery, emergency repair work, and safe methods of doing it.

➤ Maintenance of electrical installations and equipment.
➤ Safe storage, handling and, where applicable, packaging, labelling and transport of dangerous substances.
➤ Controls of work involving harmful substances such as lead and asbestos.
➤ The introduction of new plant, equipment or substances into the workplace by examination, testing and consultation with the workforce.

Other hazards
➤ Noise problems – wearing of hearing protection, and control of noise at source
➤ Vibration problems – hand-arm and whole-body control techniques and personal protection
➤ Preventing unnecessary or unauthorized entry into hazardous areas
➤ Lifting of heavy or awkward loads
➤ Protecting the safety of employees against assault when handling or transporting the employer’s money or valuables
➤ Special hazards to employees when working on unfamiliar sites, including discussion with site manager where necessary
➤ Control of works transport, e.g. fork lift trucks by restricting use to experienced and authorized operators or operators under instruction (which should deal fully with safety aspects).

➤ Ensuring that fi re exits are marked, unlocked and free from obstruction
➤ Maintenance and testing of fi re-fi ghting equipment, fire drills and evacuation procedures
➤ First aid, including name and location of person responsible for fi rst aid and deputy, and location of fi rst aid box.

➤ Giving your employees information about the general duties under the Health and Safety at Work Act and specifi c legal requirements relating to their work.
➤ Giving employees necessary information about substances, plant, machinery, and equipment with which they come into contact.
➤ Discussing with contractors, before they come on site, how they plan to do their job, whether they need any equipment from your organization to help them, whether they can operate either in a segregated area or only when part of the plant is shut down and, if not, what hazards they may create for your employees and vice versa.

➤ Training employees, supervisors and managers to enable them to work safely and to carry out their health and safety responsibilities efficiently.

➤ Supervising employees so far as necessary for their safety – especially young workers, new employees and employees carrying out unfamiliar tasks.

Keeping Check
➤ Regular inspections and checks of the workplace, machinery appliances and working methods.



It is important that the health and safety policy is monitored and reviewed on a regular basis. For this to be successful, a series of benchmarks need to be established.

Such benchmarks, or examples of good practice, are defined by comparison with the health and safety performance of other parts of the organization or the national performance of the occupational group of the organization.

The Health and Safety Executive publish an annual report, statistics and a bulletins all of which may be used for this purpose. Typical benchmarks include accident rates per employee and accident or disease causation.

There are several reasons to review the health and safety policy. The more important reasons are:
➤ signifi cant organizational changes have taken place
➤ there have been changes in personnel
➤ there have been changes in legislation
➤ the monitoring of risk assessments or accident/ incident investigations indicate that the health and safety policy is no longer totally effective
➤ enforcement action has been taken by the HSE or

Local Authority
➤ a suffi cient period of time has elapsed since the previous review. A positive promotion of health and safety performance will achieve far more than simply prevent accidents and ill-health. It will:
➤ support the overall development of personnel
➤ improve communication and consultation throughout the organization
➤ minimize fi nancial losses due to accidents and illhealth and other incidents

➤ directly involve senior managers in all levels of the organization
➤ improve supervision, particularly for young persons and those on occupational training courses
➤ improve production processes
➤ improve the public image of the organization or company.

It is apparent, however, that some health and safety policies appear to be less than successful. There are many reasons for this. The most common are:

➤ the statements in the policy and the health and safety priorities are not understood by or properly communicated to the workforce
➤ minimal resources are made available for the implementation of the policy
➤ too much emphasis on rules for employees and too little on management policy
➤ a lack of parity with other activities of the organization (such as fi nance and quality control) due to mistaken concerns about the costs of health and safety and the effect of those costs on overall performance. This attitude produces a poor health and safety culture
➤ lack of senior management involvement in health and safety, particularly at board level
➤ employee concerns that their health and safety issues not being addressed or that they are not receiving adequate health and safety information. This can lead to low morale amongst the workforce and, possibly, high absenteeism
➤ high labour turnover
➤ inadequate personal protective equipment
➤ unsafe and poorly maintained machinery and equipment
➤ a lack of health and safety monitoring procedures.

In summary, a successful health and safety policy is likely to lead to a successful organization or company.



Figure below shows the schematic diagram of an air-conditioning plant. The majority of the air is drawn from
the space, mixed with outside ventilation air and then conditioned before being blown back into the space.

Air Conditioning Plant

Air-conditioning systems are designed to meet a variety of objectives. In many commercial and institutional systems, the ratio of outside ventilation air to return air typically varies from 15 to 25% of outside air. There are, however, systems which provide 100% outside air with zero recirculation.

The components, from left to right, are: Outside Air Damper, which closes off the outside air intake when the system is switched off. The damper can be on a spring return with a motor to drive it open; then it will automatically close on power failure.

On many systems there will be a metal mesh screen located upstream of the filter, to prevent birds and small animals from entering, and to catch larger items such as leaves and pieces of paper. Mixing chamber, where return air from the space is mixed with the outside ventilation air.

Filter, which cleans the air by removing solid airborne contaminants (dirt). The filter is positioned so that it cleans the return air and the ventilation air.

The filter is also positioned upstream of any heating or cooling coils, to keep the coils clean. This is particularly important for the cooling coil, because the coil is wet with condensation when it is cooling.

Heating coil, which raises the air temperature to the required supply temperature.

Cooling coil, which provides cooling and dehumidification. A thermostat mounted in the space will normally control this coil.

A single thermostat and controller are often used to control both the heating and cooling coil. This method reduces energy waste, because it ensures the two coils cannot both be “on” at the same time.

Humidifier, which adds moisture, and which is usually controlled by a humidistat in the space. In addition, a high humidity override humidistat will often be mounted just downstream of the fan, to switch the humidification “off” if it is too humid in the duct.

This minimizes the possibility of condensation forming in the duct.

Fan, to draw the air through the resistance of the system and blow it into the space. These components are controlled to achieve six of the seven air-conditioning processes.

Heating: directly by the space thermostat controlling the amount of heat supplied by the heating coil.

Cooling: directly by the space thermostat controlling the amount of cooling supplied to the cooling coil.

Dehumidifying: by default when cooling is required, since, as the cooling coil cools the air, some moisture condenses out.

Humidifying: directly, by releasing steam into the air, or by a very fine water spray into the air causing both humidification and cooling.

Ventilating: provided by the outside air brought in to the system.

Cleaning: provided by the supply of filtered air.

Air movement within the space is not addressed by the air-conditioning plant, but rather by the way the air is delivered into the space.


What Are The Effect Of Environment On Work Safety?

The environment has a significant part to play in the capacity of the person–machine combination to produce output at the desired level and without loss. The person–machine production and safety factors are reduced by downgrading the work environment.

Environmental factors that impact on production and safe working standards include the following:

• reducing the amount of time allowed for performing the task

• abnormal temperature conditions

• failing to provide adequate lighting or proper illumination

• restrictions to movement through special clothing and equipment

• failure to provide compatible workplace design

• excessive noise and vibration

• imposing stress: lack of rest, confinement, isolation

• emotional stresses: fear, anxiety, boredom or personal issues.

Generally, a machine is not designed to operate continuously at its maximum limit. Logically, we should not design work systems which demand constant maximum output and vigilance from humans. 

Both people and machines are less prone to error where environmental variations and extremes can be avoided. Also to be avoided is the belief that, because person and machine are seen to perform well in poor environmental conditions, improvement is not needed. 

The effectiveness of procedures in ensuring suitable practices depends on training, supervision and the culture of the organization.


What Are The Different Types Of Workplace Injuries?

Some idea of the types of workplace injury can be had by studying the tables in various databases, some online. These can give a view on an occupation and industry basis

Injury rates
                                                       Frequency Rate       Average Time          Lost Rate Incidence Rate
Larger organization                                 40                           15                               9.2%
Smaller organization                                87                             3                                20%

or a view of the duration based on the nature of injury. Other duration sheets relating to bodily location, mechanism of injury and breakdown agency (e.g. tool, substance) are also available.

Another way of looking at injuries, suggested by G.L. McDonald, a Queensland safety researcher, involves dividing injury into three classes:

Class 1 Accident permanently alters the future of the individual.

Class 2 Lost-time accident where individual fully recovers.

Class 3 Accidents which cause inconvenience to the individual but do not stop him/her from carrying out normal duties.

McDonald  has produced line diagrams which graph class of injury and total cost of that class based on actual data for an OHS jurisdiction. The case for focusing prevention on Class 1 is very strong.


This rate is often referred to as the Duration Rate, and is used to indicate the severity of injury. As we saw hen discussing the Frequency Rate, we were unable to determine how serious the LTIs were because this data was not built into the formula.

By using the ATLR in combination with the Frequency Rate a clearer picture of injury performance is possible. The ATLR is calculated by dividing the number of days lost through injury by the number of LTIs.

Average Time Lost Rate = Number of days lost/Number of LTIs

A death is counted as 220 standard working days lost.


In our organization with 500 workers, who experienced 46 LTIs (see Example A), assume the following injury outcomes:

10 LTIs resulted in 3 days each 30
8 LTIs resulted in 6 days each 48
12 LTIs resulted in 14 days each 168
4 LTIs resulted in 20 days each 80
10 LTIs resulted in 28 days each 280
2 LTIs resulted in 42 days each 84

Total 690

Average Time Lost Rate = 690 days lost/ 46 LTIs = 15

As a result of this calculation we are now in a better position to assess the injury performance. We now know the organization has had 40 LTIs per million hours exposure and each injury experienced during the year resulted in an average of 15 days off work.

This additional information provides the safety and health professional with the necessary knowledge required to make decisions and recommendations on the areas of risk within the workplace where resources and effort should be directed.


The main thrust of this model is in the category of operator behaviour. It is based on Rasmussen’s theoretical work on the analysis of operator tasks. According to his model, three levels of operator behaviour may be identified.

Skill-based behaviour
This refers to routine tasks requiring little or no conscious attention during task execution. In this way enough ‘mental capacity’ is left to perform other tasks in parallel. For example: an experienced car driver travelling a familiar route will control the vehicle on a skill-based level, enabling them to have an intelligent discussion with a passenger, parallel to the driving task.

Rule-based behaviour
This refers to familiar procedures applied to frequent decision-making situations. A car driver integrating the known rules for right-of-way at crossings with stop signs or traffic lights, deciding whether to stop the vehicle or pass the crossing, is functioning at this level also.

The separate actions themselves (looking for other traffic, bringing the vehicle to a full stop, changing gears, etc.) will again be performed on a skill-based level. Making these familiar decisions and monitoring the execution of the skill-based actions requires some part of the total mental capacity available to the driver, but not all.

Knowledge-based behaviour
This refers to problem-solving activities, for instance when a person is confronted with new situations for which no readily available standard solutions exist. The same car driver approaching a crossing where the traffic lights have broken down during rush hour will first have to set their primary goal: do they want to proceed as fast as possible or do they want to minimize the chance of collision?

Depending on this goal they will control the vehicle with varying degrees of risk taking (e.g. by ignoring some of the usual traffic rules whenever they see an opportunity to move ahead somewhat). It is interesting to note that this model infers that an accident occurs as a consequence of goal setting followed by a human decision.

Any error may be attributed to human behaviour, perception, cognitive skills and experience, factors which have been widely used in other accident models.

Rasmussen has also developed the boundary theory which has particular relevance to large-scale acccidents. In this theory organizations operate in a space of possibilities within the three boundaries of economic failure, unacceptable workload and functionally acceptable performance.

Within this last boundary is the resulting perceived boundary of acceptable performance. The distance between these two is the margin for error. Rasmussen considers experiments to improve performance to create Brownian or random movements within this space.

There are pressure gradients operating, such as the gradient towards least effort, and the management pressure towards efficiency, both driving the organization in the direction of the perceived boundary of acceptable performance.

A counter gradient may exist in the form of safety culture campaigns. If corporate behaviour in the presence of strong gradients migrates past the perceived boundary and reaches the boundary of functionally acceptable performance, then an accident is likely.


Principal contributors
It is difficult to clearly identify all the forces responsible for the wave of change in work safety and occupational health. The visible indicators of change are perhaps the changed role of the government inspectorate, the safety representative and media promotion.

These signs of change represent only the curl of the wave. The real forces are far less obvious than inspectors, representatives and media promotion. Some examples are listed below.

Many educational institutions offer studies in occupational health and safety or a particular aspect of this field, such as ergonomics or occupational hygiene. These courses have led to a large increase in highly skilled and career minded professional people working in the field.

Government administration
Government departments exist to administer the occupational health, safety and welfare legislation. These departments have an inspectorate role and may also provide information, education and training services.

They are also given the responsibility to prosecute for a breach of particular legislation and the task of producing standards and codes of practice. Some also provide research grants for occupational health and safety studies.

Professional associations
The interest created by safety and health reform around the world has led to a growth in the number of people working in the field of accident prevention and health management.

Internationally, associations such as the International Social Security Association and the International Commission on Occupational Health have emerged as groups with potential for influence. A range of national professional associations also exists.

Trade unions
In many countries trade unions play an important role in securing and improving working conditions, often being represented on occupational health and safety policy making bodies. Groups such as the International Federation of Free Trade Unions also bring pressure to bear on those countries where unions are weak or non-existent.

A number of employee associations have appointed full-time health and safety officials. This is likely to increase as the employee demand for safer and healthier work environments places increasing pressure on the traditional union services and skills.

Employer groups
Employer groups and associations are usually also represented in occupational health and safety policy making bodies. Groups of employers in a particular industry sector may also develop particular approaches to health and safety relevant to that industry and provide health and safety assistance to employees in that industry sector.

International Labour Organization (ILO)
The governing body of the ILO is the International Labour Council on which employer and employee bodies and governments are represented. The ILO publishes a series of conventions and recommendations on occupational health and safety to be used as a basis for minimum standards.

These documents are well regarded, as is the ILO Encyclopaedia of Occupational Health and Safety which has become a widely used reference source.

Public pressure
Many of the industrial processes and work activities that are carried out have an effect on people both inside and outside the workplace. Escaping chemicals, noise, dust and dumping of industrial wastes are just a few examples. There is undoubtedly a strong public and media influence in the drive for safer and healthier work.

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