OCCUPATIONAL HEALTH AND SAFETY RISK CONTROL ENGINEERING STRATEGIES BASIC INFORMATION


Personal protective equipment should be the last resort in defence. Better alternatives lie in engineering controls that eliminate as much of the risk as possible. Engineering controls fall into five categories:

• substitution
• alternative work methods
• isolation
• enclosure
• ventilation.


Substitution
This control substitutes a less toxic chemical that can do the same job. A common example is the substitution of calcium silicate or fibreglass insulation for asbestos insulation. Substitution is an effective control as long as the substitute is less hazardous.

Alternative Work Methods
This simply means doing the job in a way which is less hazardous. For example, brushing or rolling paint produces much lower vapour levels than spray painting.

Similarly, wet removal of asbestos releases up to 100 times less dust than dry removal. The change should be checked to ensure that it is safer.

Isolation
Isolation isolates the worker from the hazard. In a quarry, for example, the operator of a crusher can be isolated from dust by a filtered, air-conditioned cab.

Enclosure
A substance or procedure may be enclosed to contain toxic emissions. It may be as simple as putting a lid on an open solvent tank or enclosing asbestos removal projects with polyethylene sheeting.

Enclosures have also been built around compressors to reduce the noise level. Enclosures must not restrict access when maintenance is required.

Ventilation
A common engineering control is to dilute the contaminant in the air by using general ventilation. Local ventilation is better because it removes the contaminant.

General ventilation may employ fans to move large volumes of air and increase air exchange. This is not suitable, however, for highly toxic materials.

Local ventilation captures and removes contaminants at their source. At a shop bench, a fume hood can be constructed to remove dusts and fumes. On sites, portable fume extractors can be used.

Remember: many filtering systems can only remove fumes—not gases or vapours.

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