What extremely high or extremely low fit factors tell you

Since the beginning of RAECO Rents, the most frequently rented instrument has been the TSI PortaCount quantitative respirator fit testing system, particularly in summer, when teaching hospitals take on their new classes of medical students, nurses, interns, and residents. With those frequent rentals come some common questions regarding fit factor.

What's a fit factor?

Fit factor is a numeric estimate of the fit of a particular respirator or mask to a specific person. It gives a ratio of the concentration of a substance in ambient air to the concentration that leaks into the respirator or mask during testing.

OSHA requires that people wearing full face respirators must be able to minimally achieve a Fit Factor of 500 or better. For half face masks, the fit factor must be 100 or above. Your specific industry may have more strict requirements, and require a higher fit factor. Qualitative testing systems that use Bitrex or Saccharine can only achieve a fit factor of 100 at best.

What if my fit factor is low?

There are several reasons you may get a very low fit factor, or a factor of 1.

• Your respirator may not be equipped with a HEPA, Class 99, Class 100, or P3 filter. Make sure you're using the right filter for testing
• The respirator may have leaks, loose filters, or a malfunctioning exhalation valve. Check the condition of your respirator, and repair or replace as needed.
• The Twin Tube assembly may be disconnected. Make sure it's connected properly to both the port on the fit test system and your respirator sampling port.
• The sample tube is too long. Use a standard five-foot tube. Longer tubes can prevent purging between the ambient and mask sample.
• You may have an alcohol level problem. Make sure the alcohol cartridge is properly filled and inserted tightly into your fit test system.

What if my fit factor is high?

Sometimes, you'll see a fit factor result of 100,000 or more. These suspiciously high fit factor on a full- or half-face mask can indicate a problem. Here are some things to check:

• Make sure your mask fit test adapter is correctly assembled.
• Make sure the sample tube is positioned correctly inside your mask.
• Check the sample tube to make sure it isn't twisted or blocked.
• Enable the "High Fit Factor Warning" in FitPro or FitPlus software to alert you if something might be wrong during a test. It won't stop your test, just indicate that you may want to retest or look for other issues.

If you have other questions about fit testing, check out our fit test video training series, or call 866-736-8347 and ask our team.