What are the different respirator fit test methods and which one is the best?

Respirators only work if they form a tight seal against the wearer's face. A Qualitative Fit Test can reveal whether there is any leakage in the seal.

The test is performed by releasing one of four substances in the presence of a worker who is wearing their respirator. If the wearer can detect the substance, this indicates that the respirator's seal is compromised.

• Isoamyl Acetate – Isoamyl Acetate (often referred to as banana oil) is a substance that smells like bananas. When using this method, the employee should first be exposed to the banana oil without their respirator to ensure that they are able to clearly detect its smell. Note that Isoamyl Acetate is not recommended for testing particulate respirators.
• Saccharin and Bitrex – Saccharin and Bitrex are aerosols that either taste sweet (Saccharin) or bitter (Bitrex). It is important to establish a baseline and test whether the employee can taste the substance before testing it with the respirator. The wearer should not chew gum, drink anything other than water, or eat for at least 15 minutes prior to performing this test.
• Stannic Chloride – Stannic Chloride is used to produce smoke that irritates the eyes, lungs, and nasal passages. When using this method, employees should only be exposed to a small amount of the smoke to ensure they don't have an excessive or unfavorable reaction to it.

All four options are acceptable and left to the preference of the tester or the company. Which option is best usually depends on the individual workers whose respirators you are testing. If, for instance, a worker is unable to detect the smell of banana oil when exposed to it without the respirator, the test will need to be performed using another method. Likewise, Saccharin or Bitrex will be inadequate for testing the fit on any employee who is unable to detect sweet or bitter tastes (perhaps due to an injury or illness).