HSE Researchers Examine Sampling Port Location for Particle-Counting Fit Tests

A new study published by Britain’s Health and Safety Executive (HSE) examines the effect of different sampling port locations during fit testing of filtering facepiece respirators using an ambient particle counting method. While HSE advises that the sampling port be extended inside the respirator to ensure the sample is taken from the wearer’s breathing zone, many fit tests are conducted with the sampling port flush with the inside surface of the respirator, according to the study. HSE researchers sought to determine if using the “flush port” for fit testing was acceptable.

Researchers tested four different models of filtering facepiece class 3 (FFP3) respirators, which have a minimum filtration percentage of 99 percent. Results indicated that the minimum exercise fit factor given by flush-port fit tests was 17 percent higher than that obtained by fit tests using the extended port. Similarly, the overall fit factor for the flush-port fit tests was 16 percent higher than for the extended-port fit tests.

The study concludes that this difference “is unlikely to affect the outcome of a fit test” except in cases where the result is close to a fit factor of 100, which HSE has set as the pass level for filtering facepiece respirators. According to the study, “an individual who passes with a result of 115 using the flush port, may have failed with a result of 99 using the extended port,” an outcome that would represent “a false pass.”

For more information, access the study on the HSE website.

In the United States, OSHA-accepted fit test protocols are described in Appendix A of the personal protective equipment standard. The protocol for generated aerosol quantitative fit testing specifies that the probe should extend at least one-quarter inch inside the facepiece cavity.