Do N95 Masks Stop COVID? OSHA Drops Some Respirator Knowledge

Frank Ferreri

Washington, DC ( – If knowledge is power, the Occupational Safety and Health Administration’s regular updating of its COVID-19 guidance seeks to keep employers in a position of authority when it comes to pandemic safety.

In its latest addition to the guidance, OSHA gave a crash course on N95 respirators, how they work, and why they’re effective against the novel coronavirus that’s changed workplaces across the world. Here’s a look at what the agency covered.

Size Matters

Some have said that because the virus is approximately 0.1 microns in size, no respirator – N95 or not – will offer protection. OSHA explained that this kind of commentary misunderstands how respirators function.

“The virus is part of larger particles that are made up of water and other materials such as mucus,” OSHA explained. “These larger particles are easily trapped and filtered out by N95 respirators because they are too big to pass through the filter.”

Talking, coughing, and sneezing sends out airborne particles that contain more than just the virus, so an N95 respirator’s mechanical filtration prevents these particles from getting through as the wearer breathes.

But Not Just Mechanical Filtration

In addition to the filtration process, N95 respirators create an electrostatic charge that attracts particles to fibers in the filter, where particles become stuck.

Additionally, OSHA slipped a little physics into the guidance, explaining that thanks to Brownian motion, the smallest particles constantly move around and are “very likely to hit a filter fiber and stick to it.”

So Just How Small?

The National Institute for Occupational Safety and Health tests respirators using particles that are 0.3 microns in diameter. If worn correctly, an N95 respirator will filter out at least 95 percent of particles of this size. OSHA explained that the respirators aren’t limited by the 0.3 number.

“An N95 respirator is more effective at filtering particles that are smaller or larger than 0.3 microns in size,” the agency wrote.

Using Respirators Correctly

Safety tools are only as good as the people and policies that put them in the hands of workers, and N95 respirators are no exception.

OSHA noted that NIOSH-approved respirators of all kinds can be “very effective” at protecting people from COVID-19 under the right conditions.

“It is important for employers and workers to remember that the respirator only provides the expected protection when used correctly,” OSHA highlighted. “Respirators, when required, must be used as part of a comprehensive, written respiratory protection program.”

What should such a program look like? It must meet the requirements of OSHA’s respiratory protection standard and include:

  • Medical evaluations.
  • Training.
  • Fit testing.

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