The two main types are air-purifying respirators (APRs) and supplied-air respirators (SARs).
Air-purifying respirators can remove contaminants in the air that you breathe by filtering out particulates (e.g., dusts, metal fumes, mists, etc.). Other APRs purify air by adsorbing gases or vapours on a sorbent (adsorbing material) in a cartridge or cannister. They are tight-fitting and are available in several forms:
· mouth bit respirator (fits in the mouth and comes with a nose clip to hold nostrils closed - for escape purposes only)
· quarter-mask (covering the nose and mouth),
· half-face mask (covering the face from the nose to below the chin), or
· full facepiece (covering the face from above the eyes to below the chin).
Respirators with a full facepiece also protect the eyes from exposure to irritating chemicals.
Supplied-air respirators (SARs) supply clean air from a compressed air tank or through an air line. This air is not from the work room area. The air supplied in tanks or from compressors must meet certain standards for purity and moisture content (e.g., CSA Standard Z180.1-00 (R2010): Compressed Breathing Air and Systems).
Supplied-air respirators may have either tight-fitting or loose-fitting respiratory inlets. Respirators with tight-fitting respiratory inlets have half or full facepieces. Types with loose-fitting respiratory inlets can be hoods or helmets that cover the head and neck, or loose-fitting facepieces with rubber or fabric side shields. These are supplied with air through airlines.
Examples of these classes of respirators include:
Air-purifying respirators (APRs):
· particulate respirators (previously called dust, fume, and mist respirators or masks),
· chemical cartridge respirators that can have a combination of chemical cartridges, along with a dust prefilter: this combination provides protection against different kinds of contaminants in the air
· gas masks (contain more adsorbent than cartridge-type respirators and can provide a higher level of protection than chemical cartridge respirators)
· powered air-purifying respirators (PAPRs).
Supplied-air respirators (SARs):
· self-contained breathing apparatus (SCBA),
· airline supplied-air respirators,
· protective suits that totally encapsulate the wearer's body and incorporate a life-support system.
There are some combinations of airline respirators and SCBAs that allow workers to work for extended periods in oxygen-deficient areas or where there are airborne toxic contaminants. The auxiliary or backup SCBA source allows the worker to escape with an emergency source of air if the airline source fails.
There are also combination air-purifying and atmosphere supplying respirators. These will offer worker protection if the supplied-air system fails, if the appropriate air-purifier units are selected. These cannot be used in oxygen-deficient areas or where the air concentration of a contaminant exceeds the IDLH level (i.e., immediately dangerous to life or health).
Since filters capture particles, caution must be exercised to always check that these filters are not clogged as it makes it harder for air to pass through and increase the likelihood of contaminated air entering the mask. Cartridges can also become "full" or saturated. It will stop working and "breakthrough" will occur – this term means that the gases or vapours will leak through the cartridge. Both cartridges and filters must be replaced on a regular basis by using the manufacturer’s recommendations (usually determined by using warning properties or end-of-service indicators).
There are 9 classes of particulate filters, depending on the particulate material. They are also classified based on levels of oil resistance and filter efficiency. Oil can break down certain types of filters which means it is important to know the materials you are working with at all times and always select the right cartridge for your respirator.
The main categories are:
· N series (Not resistant to oil) - May be used in any atmosphere where there is no oil particulate.
· R series (Resistant to oil) - May be used in any atmosphere where there is no oil particulate, or up to one shift where there is oil particulate present. "One shift" means eight hours of continuous or intermittent use.
· P series (Oil-Proof) - May be used in any atmosphere, including those with oil particulates, for more than one shift. If the filter is used in atmospheres with oil particulates, contact the manufacturer to find out the service life of the filter.