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The fifth step of the COSHH assessment requires the employer or authorised persons to ensure that the methods employed to control exposure actually work in practice.

Even when the control measures are used as instructed (and you, the employer, have evidence to this effect), do you actually know:

  • That the control measures are in good repair?

  • That they actually achieve the planned reduction in the level of exposure?

Exposure through Direct Contact

Where the hazardous substance is a solid or liquid and potential exposure is to the skin or eyes only, personal protective equipment would usually be expected to achieve the desired control. In these cases, measurement is not normally necessary. 

Exposure Through Inhalation

However, if potential exposure is by inhalation, and over extended working periods then COSHH requires that the concentration of hazardous substances in the air should be measured (monitored), a task that requires specialist air-monitoring equipment.

Monitoring of concentrations of hazardous substances in the air, particularly where workers can be exposed over long periods, is especially important:

  • If deterioration or failure of the methods of control would be a serious risk to health;

  • Where there is doubt that the method of control is working properly

  • Where there is doubt that the exposure limits are being achieved even with the control method in place

It should be noted that records for the maintenance of control measures such as the periodic testing of local exhaust ventilation (LEV; air extraction) and of any exposure monitoring carried out must be maintained for at least five years.

The potential for exposure by inhalation over extended working periods is the basis for monitoring air space. In the case of our crime scene examiner, exposure to the powder is periodic, though at times can be extensive. It is unlikely that our examiner would be exposed to the powder over extended working periods as would be the case of a person working in an aluminium milling factory. Nevertheless, it is certainly true that when an crime scene examiner has been extensively using aluminium powder, the evidence that they have been doing so is more often than not "written across their face" in the form of a silvery coating on and around their face mask.

In assessing the likelihood of exposure, we do not believe there is any merit to monitoring the airspace on a routine, scene-by-scene basis. This would be entirely impractical. What seems much more sensible is to ensure that no aluminium powder is able to creep around the edges of the face mask, or through imperfections, should there be any [the choice of mask is therefore an important consideration
]. If after leaving a scene the examiner finds that quantities of the dust have passed around or through the mask, it is clear that the mask is unsuitable or an imperfect fit. This should be noted, and the question of choice of mask revisited.

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