The COSHH Regulations reg.7(1), The CLAW Regulations reg.6(1), The CAW Regulations reg.10(1)(a) place the duty on the employer to prevent the exposure of their employees to hazardous substances; where prevention of exposure is not reasonably practicable, the employer must reduce it to the lowest concentration reasonably practicable by means other than the use of RPE.

If, despite the use of suitable control measures (i.e. other than RPE) adequate control of exposure cannot be achieved, employers must provide suitable RPE (COSHH Regulations reg.7(3)(c), CLAW Regulations reg.6(3)(c), CAW Regulations reg.10(4)). The RPE provided must reduce the exposure to a concentration that is as low as reasonably practicable, and in any case below any applicable exposure or control limits.

The ACOPS 1, 2, 3, 4 supporting the COSHH, CLAW and CAW Regulations recommend that the initial selection of tight fitting facepieces should include a fit test. This is to ensure that the selected RPE has the potential to provide adequate protection for the wearer (L5 para 148, L27 para 79, L28 para 81 and L132 para 133). The circumstances where repeat fit testing is needed are referred to in L5 para 149, L27 para 80, L28 para 82 and L132 para 134.

The employer must have documented evidence of the characteristics of the RPE to be used (CAW reg.7(3)(d)). Similar requirements are described in COSHH reg.6(4), and CLAW reg.5(4). These requirements are there to ensure that the RPE provided is suitable. The evidence to support the suitability will include fit test reports for facepieces with tight-fitting face seals. Fit test records should be retained by the employer and must be kept available for inspection on request.