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There's more to respirators than meet the eye

By Michelle Morra

Respirator technology is light years away from the makeshift devices created during World War I to protect soldiers from mustard gas. Not only have manufacturers learned how to keep out harmful substances and particles, but in their quest for a tight seal against the wearer’s face, their materials have evolved from rigid forms of rubber to softer, more resilient materials that mold to the face.

Respirators are better than ever but have yet to achieve the ideal: locking out airborne contaminants 100 per cent of the time for 100 per cent of wearers.

No two faces are alike, and with North America’s increasingly diverse workplace, respirators must fit a growing variety of facial shapes and sizes.

For all applications that require tight-fitting respirators for protection from hazardous airborne contaminants, a tight seal is necessary. That’s why jurisdictions in the U.S. and Canada mandate that workers be fit-tested when they wear these face-seal dependent respirators.

There are two broad categories of tight-fitting respirators. Air-purifying respirators remove contaminants in the air we breathe by filtering out particulates, or by absorbing gases or vapours in a cartridge or canister. Supplied-air respirators supply clean air from a compressed air tank or through an air line; their inlets can be either tight-fitting or loose-fitting. 

Health and safety legislation requires fit-testing every two years, and recommends it be done annually. A quantitative fit test, where a high protection factor is needed, measures the adequacy of a respirator’s fit by numerically measuring the amount of leakage into the respirator. For less protective needs, a qualitative fit test is a pass/fail test that relies on the employee’s response to a test agent, such as a strong smell.

Testing is key
Fit-testing must be done by a competent person using the right equipment. It usually happens at the work site, but can be outsourced to the manufacturer or other fit-test provider. Mobile fit-testing services, which come to the worksite, are useful for workplaces in remote locations. 

Besides the bi-annual fit-testing required by law, respirator wearers should be trained to check the seal every time they put on a respirator. This requires no special equipment and is easy to do, but the procedure depends on whether the respirator is positive-pressure or negative-pressure.

From one work shift to the next, a respirator can sustain damage. The wearer’s face, too can change. Illness, stubble, acne, dirt or grime — all of these factors can affect the seal. Failing to test it daily can help prevent a false sense of safety. This “fit check,” however, is not a substitute for qualitative or quantitative fit-tests.

As legislators update their laws and guidelines, manufacturers, employers and workers must keep up with the new requirements. The changes — all in the name of safety — affect some workplaces more than others.

When the Centers for Disease Control and Prevention and the California Department of Public Health (CDPH) recognized last spring that the H1N1 Influenza A virus might become a public health threat, they recommended controls to protect health-care workers, including “the use of respirators at least as effective as a fit-tested N95 filtering facepiece respirator” when in direct contact with a patient who might have the illness.

California continued to see H1N1 cases and some facilities were running out of respirators, so the state and federal governments provided a stockpile of respirators.

On January 2010, CDPH recommended discontinued use of one particular respirator, 3M’s 8000 model, because it had a low success rate in fit-testing.

In an update published on its website, the National Institute for Occupational Safety and Health (NIOSH) says the issue stemmed from a report from a “California health care institution” saying that “in a high percentage of cases, the institution was unable to adequately fit the model 8000 N95 respirators to intended users in required fit-tests.”

In an interview, Jackie Berry, a 3M spokesperson, says the population used in this particular instance to fit-test the model 8000 respirator “was very limited” and notes that 3M manufactures various models of N95 respirators with various features that affect fit and worker comfort.

“Because we all have individual facial characteristics, they’re diverse, respirator features will have a unique impact on performance from individual to individual,” Berry says.

She adds, “The 8000 model respirator works as intended —there are no performance issues with the product.”

There is no manufacturer recall on the 3M model 8000 respirators.

On its website, NIOSH notes that 3M’s model 8000 respirator is certified, which means it meets current NIOSH testing criteria such as filtration efficiency and breathing resistance. Its current criteria, however, does not include an evaluation for fit.  

Following a request from the California Department of Occupational Safety and Health, NIOSH conducted tests on the model 8000 respirators and found that the products pass NIOSH requirements for filtration and inhalation/exhalation resistance.

Its visual examination also “showed no problem with the respirators,” and a review of 3M’s production quality control documents indicates “quality assurance plan for manufacture of the respirators has been followed and no non-compliance issues were observed.”

As of this writing, NIOSH is conducting fit-testing evaluation for the model 8000, to determine if it “poses any abnormal or unusual characteristics in achieving face-seal fit among subjects on the NIOSH fit-test panel.”

New rule

Meanwhile, manufacturers are also keeping a close eye on an upcoming change in the fit-testing requirements of NIOSH. The new rule specifies total inward leakage (TIL) minimum performance requirements and testing to be conducted by NIOSH and respirator manufacturers to demonstrate that these respirators, when selected and used correctly, provide effective respiratory protection to intended users against toxic dusts, mists, fumes, fibres as well as biological and infectious aerosols, including influenza A (H5N1) and SARS.  

Under current NIOSH legislation, disposable respirator masks are not required to undergo fit-testing, but the proposed rule published by NIOSH in October 2009, under 42 CFR Part 84, applies exclusively to half-mask air-purifying particulate respirators, including both elastomeric facepiece and filtering (disposable) facepiece types.

Canada references NIOSH in its regulatory standards and guidelines. 

“I guess they’re saying to themselves, we need a more stringent test,” says John Hierbaum, product line manager for air-purifying respirators at MSA. “Over the last three or four years, NIOSH tested a large number of approved respirators on the market and they had a very high failure rate.”

Hierbaum believes the NIOSH proposal is a good move because it puts all half-mask respirators with the same assigned protection factor in the same ballpark.

Michelle Morra is an award-winning writer and former COS editor. You can contact her via e-mail at


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