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6. Control

Control of Exposure Presentation

Control of Exposure Key Points

The nature of the health effects of exposure to RCS mean that exposure should be controlled to a low a level as possible and always below the OEL. With any given workplace there are always a range of possible control measures that could be used. The risk assessment should be used to help to decide what control methods will be best for the workplace being investigated. The choice of control methods to be used should be based upon application of the control hierarchy, the cost of the control methods balanced against the cost of implementing them, and the usability and practicality of those methods in the work environment. 

The basic control hierarchy involves choice of control measures from a series of approaches based upon the effectiveness of control. This approach emphasises the need to control the dust at source before considering means of reducing spread of the dust and finally how we can protect individual workers from exposure.

The first in this series of approaches to control is elimination of the hazard. Unfortunately there are few work environments where RCS can be completely removed as it is either naturally present or integral to the work process. If the RCS cannot be completely eliminated from the work environment substitution should be considered. 

In some circumstances it may be possible to substitute RCS with a less hazardous substance such as replacing silica sand used in shot blasting processes with less hazardous materials such as metal beads. It may also be possible substitute a process generating RCS dust with one that is less dusty. The most common example of this approach is to move from a dry process to a wet process. This can be as simple as wetting dusty surfaces or the use of water when cutting or drilling crystalline silica containing materials. With this approach it is important that the wetted dust is not allowed to dry out in the work environment as once dry the RCS dust can then re-enter the workplace air. 

The next control approach to consider is the use of engineering controls. The most effective engineering controls will remove the RCS dust at its source before it can enter the workplace air. Such controls need to be carefully designed to ensure they effectively capture the dust. These controls work by either completely enclosing the source of dust or by drawing the dust away using local exhaust ventilation (LEV) systems. Once the dust is in the workplace air it may be possible to use mechanical ventilation to dilute the airborne concentration of RCS down to an acceptable level.  As the concentration of dust is likely to vary throughout the work environment dilution ventilation may not be adequate to protect all of the workers and further controls to protect the effected workers may be necessary. Mechanical controls can also be used to protect individual workers or groups of workers by isolating the workers from the dust containing air. This normally involves placing the workers in an enclosed cab that is provided with filtered air.

In circumstances where there is no alternative means of controlling exposure respiratory protective equipment (RPE) can be used. RPE should not be considered as an acceptable control if other more effective control measures are possible. RPE will only provide adequate control if an appropriate type RPE is used, the RPE is used correctly and it is maintained and replaced when required. RPE should only be used by workers trained in its use and who are under adequate supervision to ensure that it is used correctly.

Answer the questions below to test you understanding of the subject.

Select the correct answer for each of the questions below to test your understanding of the subject.


Which of the following methods is the most effective means of controlling exposure during shot blasting operations?


Respiratory Protective Equipment (RPE)

Dilution ventilation

Local exhaust ventilation (LEV)

Substitution of silica sand with a less hazardous material



When cutting concrete with a masonry saw on a construction site the best means of controlling exposure to RCS dust is:


Local exhaust ventilation (LEV)

Respiratory Protective Equipment (RPE)

Respiratory Protective Equipment (RPE) with wet cutting

Natural ventilation


Fill in the missing words.

Read the paragraph below and fill in the missing words.

A local exhaust ventilation (LEV) system consists of a that draws the contaminated air into a and through to take it away from the worker.

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Is this true?

Decide if the following statement is true or false.

Question 1

A simple dust mask will provide adequate protection from RCS exposure in most cases.

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