The performance of respiratory protective equipment in the workplace is normally described in terms of the protection factor (PF), which is the ratio of the airborne concentration of pollutant outside the device to that inside the device. British Standard BS4275 (BSI 1997) assigns PF values (the "assigned protection factor" or APF) to a range respiratory protective devices. (The APF is the PF that can realistically be assumed to be able to be achieved by 95% of wearers given reasonably practicable levels of training and supervision).
This report is primarily concerned with the performance of power assisted full facepiece respirators, the current APF for which is 40. This APF is based mainly on the results of "workplace protection factor" studies, particularly the work of Howie et al (1996).
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