Methods of Fit Testing:
Qualitative: This method is a basic form of fit testing. A user will put on a respirator of any design, and the tester will then run them through a series of simple yet thorough tests to make sure the fit is good. First, the user will instruct the user to place the respirator on their face with one strap going above the ears toward the top of the back of the head, and the other toward the base of the head. The tester will tell the user to make sure the seal around the nose is tight by pinching it and pressing it against the bridge of the nose. Then, the tester will ask the user to ensure a tight seal by placing their hand over the mask cartridges, or the mask itself (in the case of an N95 particulate dust mask) and breathe in. The tester will look to see if the sides of the mask suction to the face of the user, and if they do not, then the mask may be too big. Then, the tester will administer simple tests like asking the user to speak for approximately 1 minute and ask them after if the mask shifted during speech. They will ask the user to move their head in a full range of motion and ask again if the mask shifted. If the user thinks all is well with the mask, then the mask is likely to have a good seal. In the case of full face or half face cartridge respirators, the tester may also use a compound with a pungent odor to determine if the seal is good enough because if the odor reached the nostrils, it is likely that their is a breach in the seal.
Quantitative: This is a method of testing which supplies fit test values for various tests associated with overall respirator fit testing. The tests include: normal breathing, deep breathing, moving head side to side, moving head up and down, talking, grimacing, bending over, and finally normal breathing again. In order to accurately perform a fit test (I did this using a PortaCount Pro) you need to calibrate the machine to the ambient air by attaching a sampling train of a tube and a calibration filter and let the machine run through its calibration steps. Also, there is a cartridge in the machine that needs to be saturated with alcohol to ensure the machine runs properly. After that, the test subject must apply the mask and attach it to the sampling train attached to the test air (non ambient) side of the PortaCount Pro. Then the subject puts on the mask and runs through the tests. ANZI, OSHA, and NFPA (in the US) have different required fit factor values based on different mask styles and uses. The link to this table will show the specified values for each mask style.
Mask Styles: There are many mask styles. The 2 most important styles are ambient and supplied air. These are the 2 branches that every other mask style comes from. Some masks are full face, some are half face. Some are cartridge filtered (cartridges can be for chemicals, particulates, and other toxins) while others are directly supplied with oxygen. Even more basic are the N95 style particulate dust masks which you will often see contractors or carpenters wearing because they are exposed to wood and gypsum dusts regularly.
http://www.tsi.com/uploadedFiles/_Site_Root/Products/Literature/Application_Notes/ITI-046.pdf
https://www.osha.gov/video/respiratory_protection/fittesting_transcript.html
http://www.3m.com/3M/en_US/safety-centers-of-expertise-us/respiratory-protection/fit-testing/
