Fit Testing Respirators

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All respirators that rely on a mask-to-face seal must be fit tested to validate the seal is air-tight. This fit test must be performed:

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  • prior to first issue
  • when there’s a change in the model, style or size of respirator used
  • when there’s a physical facial change in the person wearing the mask
  • at least annually

Guiding Regulation: (OSHA’s) Respiratory Protection Standard, 29 Code of Federal Regulation (CFR) 1910.134 Appendix A – Fit Testing Procedures (Mandatory)

There are two categories of Fit testing – Qualitive and Quantitive

Qualitative fit testing is a pass/fail method used on half-masks that relies on senses – such as taste and smell – to detect air leakage from your respirator. The half masks being tested much have an overall fit factor (mask particle concentration divided by the ambient particle concentration) of 100 or less. The test relies on a harmless, yet bitter-tasting chemicals called Bitrex, which will determine whether you pass. Rather than measuring the amount of leakage into the facepiece, the qualitative fit test determines whether the facepiece is in working order. Unfortunately, if you taste a bitter substance, it is a fail.

The following mandatory qualitative fit test protocols (OSHA) are recognized test agents :

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  1. Isoamyl Acetate (Isopentyl Acetate or Banana Oil) This qualitative fit test agent uses a person’s response to fruit-like banana aroma to detect leakage into the respirator. A drawback to this agent is lack of a strong reaction in some fit test subjects to the banana odor. Another drawback is it can only be used with respirators equipped with organic vapor cartridges.
  2. Saccharin Solution This qualitative fit test agent uses a person’s response to a sweet taste to detect leakage into the respirator. The drawback to this agent is lack of a strong reaction in some test subjects to a sweet taste.
  3. Bitrix™ (Denatonium Benzoate) This qualitative fit test agent uses a person’s response to a bitter taste to detect leakage into the respirator. The advantage this agent has over Isoamyl Acetate and Saccharin is the bitter taste. Few enjoy a strong bitter taste so an unavoidable response by the test subject is readily noticed.
  4. Irritant Smoke (Stannic Chloride) This qualitative fit test agent uses a person’s response to the irritating chemicals released in the “smoke” produced by a stannic chloride smoke tube to detect leakage into the respirator. The stannic chloride reacts with humidity producing a white smoke with a pungent odor. The drawback to Irritant smoke is that it can be toxic. The smoke contains two compounds: hydrogen chloride (HCl) and tin (Sn). Hydrogen chloride is highly corrosive to human tissue. Inhalation of a relatively low concentration will cause irritation to the upper respiratory tract and eyes. This is why it’s such an effective chemical to use for respiratory fit testing.

Fit Test Exercises

Before beginning the qualitative fit testing protocol, employees are given a description of the fit test and their responsibilities during the procedure. All four qualitative fit test protocols use these seven, 60-second exercises:

  1. Normal breathing: – standing position without talking.
  2. Deep breathing – standing position without talking, breathing slowly and deeply.
  3. Turning head side-to-side – standing position, slowly turning head side-to side, holding at extreme point and inhaling.
  4. Moving head up and down – standing position, slowly moving head up and down and inhaling in the up position.
  5. Talking –  talk out loud slowly and loud enough to be heard clearly; read from a prepared text count backward from 100 or recite a memorized poem.
  6. Bending over/jogging in place –  bend at the waist as if to touch toes. Jogging in place is substituted for testing done in a shroud that does not permit bending over at the waist.
  7. Normal breathing – standing position without talking.

Even though these qualitative fit testing agents can be used to fit test both half-mask and full-face respirators, it is important to note that qualitative fit tests only validate an assigned protection (APF) of 10. OSHA has established an APF of 50 for full facepiece respirators, but in order to use a full facepiece beyond 10 times the permissible exposure limit (PEL), a quantitative fit test must be performed.

Quantitative fit testing is the process to measure the precise amount of leakage into any tight-fitting facepieces. Instead of relying on bitter-tasting chemicals and your senses, the test is performed by a machine calculating the measurements. Typically, the facepiece is attached to a probe, which is connected to the measuring machine by a hose. According to OSHA regulations, there are three acceptable quantitative fit test methods: 

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  1. Generated aerosol uses an aerosol, typically corn oil, that is dispensed in a high concentration into a booth or test chamber and a photometer based aerosol detector that measures the challenge agent that leaks into the face piece. This type of quantitative fit testing is the least used of the three types due to the large size of the unit and the high maintenance involved in cleaning the booth and the components.
  2. Ambient aerosol condensation nuclei counting (CNC) instruments, use laser technology to measure aerosol concentrations inside and outside the respirator without the person having to stand in a test chamber or booth. The challenge agent measured consists of ambient microscopic dusts and aerosol particles that are in the air we breathe every day. The particle concentration outside the respirator is measured against the concentration inside the respirator. The ratio of these two numbers is the fit factor.
  3. Controlled negative pressure (CNP) systems,  equipment, create a fixed vacuum on the face piece by temporarily cutting off the breathing air with special adapters. The instrument measures the airflow, or leak rate, needed to maintain the vacuum on the mask. The fit factor is then computed by taking an average breathing rate and dividing that number by the measured leak rate. The person being fit tested must remain motionless for the 10 seconds needed to conduct the test. OSHA also requires CNP fit testing to include its REDON protocol. This protocol includes exercises performed facing forward and bending over, shaking the head and two re-donnings of the respirator face piece.
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All three OSHA-accepted quantitative fit tests require the face piece being tested to be equipped with high-efficiency particle filters (P100/HEPA) so that no particles enter the respirator and skew the results. Test equipment has an N95 companion, which is used to fit test 95 filter-class respirators. The mask is also equipped with a temporary probe adapter or the person being tested might wear a surrogate mask with a permanent sampling probe. OSHA notes the employer must also ensure that persons administering the quantitative fit tests are able to calibrate the equipment used and perform tests properly, recognize invalid tests, calculate fit factors properly and ensure that test equipment is in proper working order.

Also, all three tests use these eight 60-second exercises:

  1. Normal breathing
  2. Deep breathing
  3. Turning head side to side
  4. Lifting head up and down
  5. Talking out loud
  6. Grimacing (15 seconds)
  7. Bending and touching toes (or jogging in place)
  8. Normal breathing