Respirator fit test

The fitting characteristic of a respirator is the ability of the mask to separate a worker's respiratory system from ambient air.

Scientific studies have shown that if the mask size and shape is correctly fitted to the employees’ face, they will be better protected in hazardous workplaces.

[3] These measurements showed that in practice, the effectiveness of negative pressure tight fitting respiratory protective devices (RPD) depends on leakage between mask and face, rather than the filters/canisters.

[4] This decrease in efficiency due to leakage manifested on a large scale during World War I, when gas masks were used to protect against chemical weapons.

The Russian army began to use short-term exposure to chlorine at low concentrations to solve this problem in 1917.

[7] Later, industrial workers were trained in gas chambers in the USSR (in preparation for the Second World War),[8][9][10] and late[11]'.

These methods use the reaction of workers to the taste or smell of a special material (if it leaks into mask) - gas, vapors or aerosols.

A qualitative fit test starts with an unfiltered/non-respirator sampling of the substance of choice to verify that the subject can detect it accurately.

[20][21][22][23] Recently OSHA approved a Fast Fit Protocol which enables the AAC/CPC (Ambient Aerosol Concentration/Condensation Particle Counting) method to be performed in less than three minutes.

The major advantage of the AAC/CPC method is that the test subject is moving and breathing while the fit factor is being measured.

Using a challenge pressure of 53.8 – 93.1 L/min, the CNP devices stress the mask as an employee would while breathing heavily under extreme physical conditions.

[citation needed] The CNP Method of fit testing is OSHA, NFPA and ISO certified (among others).

U.S. law began to require employers to assign and test a mask for each employee prior to assignment to a position requiring the use of a respirator and thereafter every 12 months, and optionally, in case of circumstances that could affect fit (injury, tooth loss, etc.).

The main advantage of qualitative fit test methods is the low cost of equipment, while their main drawback is their modest precision, and that they cannot be used to test tight-fitting respirators that are intended for use in atmospheres that exceed 10 PEL (due to the low sensitivity).

Multiple masks must be examined to find the "most reliable", although poor test protocols may give incorrect results.