OHD Blog

Air Not Aerosol

Jun 5, 2019

Let’s talk about fit testing. Fit testing should identify a mask that best suits you, and this includes it being suitable for your job. When you go to fit test your mask, the most important part is walking away with the confidence that it will protect you against the respiratory hazards you face at work. This means you want the most rigorous, most protective, and most accurate means of fit testing your mask.

There is no better way to do this than to directly measure any leaks. This is what the Quantifit does. Using state of the art Controlled Negative Pressure, the Quantifit pulls a negative pressure inside your mask, and to keep the pressure constant, it must pull out any additional air that leaks into the respirator. This measurement tells you how much air has leaked into the respirator, and this is converted into a fit factor. This does not mean the fit testing process has to be longer. The Quantifit offers the fastest quantitative fit test available.

Other methods use particles (Ambient Aerosol) to indirectly measure leakage. This introduces all sorts of problems. First off, not all respiratory hazards are particles. Gases like hydrogen sulfide and carbon monoxide, exist in a shapeless state that incorporates with air creating a toxic breathing environment. The hazardous gases trapped in a confined space are not particles. Vapors like toluene and mineral spirits diffuse into a gas commingling with air. Toxic vapors emanating from the after-fire environment are not particles. However, if you use air as the challenge agent, you are testing the true fit of your mask. If air can get in the mask, then there is a chance that gases and vapors can as well.

Particles also come in all shapes and sizes and the aerosol methods only test a range of those. Most coal dust particles for instance, even those within the respirable range, are not within the range that the Ambient Aerosol method can measure. Particles move within air and can be subject to drift or streamlining. The placement of your probe or the location of the leak can all impact what the ambient aerosol method will pick up. The Ambient Aerosol method of fit testing is only telling you if certain particles, within the sampling range, are near the probe within the mask. This means you are dependent on the environment around your testing site having enough of the correct size particles to test. The Quantifit can test in any environment where air is present.

Why test your mask with a method that cannot even say whether your mask is protecting you against the respiratory hazards you may encounter? Challenge your mask with air. The air that gases exist in, vapors commingle with, the air that mists and particles suspend in. Test your mask. Test with confidence.

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