Meaningful workplace protection factor measurement: experimental protocols and data treatment

Abstract

Workplace performance measurement of respiratory protective equipment (RPE) is fundamental to the understanding of how well wearers are protected. It forms the basis for guidance on which the selection of appropriate equipment is based. However, the measurement of this performance is open to many sources of interference and inaccuracy, reducing the value and relevance of the results, and is most difficult for devices providing the highest levels of protection. In this paper, a method for critically assessing collected workplace protection factor (WPF) data is validated. This method rejects unreliable data, using criteria based on the detection limits of the analytical measurement system. An iterative approach is also described which arrives at a supportable estimate of given non-parametric percentiles of the distribution of measured WPFs [such as the fifth percentile, conventionally taken to be the assigned protection factor (APF)]. Further pragmatic criteria, based on a combination of experimental experience and consideration from first principles, are suggested as the basis for any future studies of RPE performance. These will maximize the chances of valid measurements being made, and also provide insight into the level of confidence which can be placed on any of the results. A consequence of these criteria is that typical working environments and measurement methods are incapable of generating WPF data which can be considered reliable.