In order for someone to wear a respirator around the workplace, they must first make sure the respirator works for them. There are two tests that must happen before ever wearing a respirator for the first time: a fit test and a seal check.
OSHA's respiratory protection regulations require that employees be fit-tested before the initial use of a respirator and whenever a different respirator (size, style, model, or make) is used. Basically, it is exactly what it sounds like, you need to make sure the mask you will be using fits you correctly in order to provide the protection it is designed to give. There are two different types of fit testing: qualitative and quantitative.
Qualitative fit testing answers the question "Does it work?" simply in a yes or no answer. Two of your senses will be used in this test in whether you can taste or smell a substance. The only four qualitative fit-test methods accepted by OSHA include isoamyl acetate (smells like bananas), saccharin (leaves a sweet taste in the mouth), bitrex (leaves a bitter taste in the mouth), and irritant smoke (can cause coughing). In any of these instances, if the wearer can smell or taste the substance being used, the fit-test is a fail and that respirator is considered unwearable for that person.
Quantitative fit testing answers the question "If it fails, how badly does it fail?" With this type of testing, a machine is used that will be attached to the respirator with a probe that can detect amounts of particular substances as well as air pressure. OSHA recognizes three quantitative fit-test methods: generated aerosol, ambient aerosol, and controlled negative pressure. The machine will be able to detect a leak as well as how bad the leak is. If the leak is barely noticeable, the mask can be resituated in order to try the test again. If the mask still fails, it is deemed unwearable for that person.
The person wearing a respirator is required to conduct a seal check each time a respirator is worn in order to ensure the protective qualities of the respirator. The wearer can either conduct a positive pressure or a negative pressure check. In a positive pressure seal check, the wearer will exhale while blocking the paths air would normally escape in order to make sure pressure builds up within the mask before outward leakage occurs. A negative pressure seal check requires the wearer to inhale while covering the normal air entering the path into the mask in order to make sure the facepiece collapses slightly under pressure.
THESE TWO ARE NOT INTERCHANGEABLE
A fit test MUST be performed by each person and for each individual variance of masks provided before ever wearing a respirator. This fit-test must be completed each year after the initial fit-test. Seal checks must be performed EACH time a mask that has already passed the fit-test is worn. Seal checking must not take place of a fit test.