Cartridges and canisters of air-purifying respirators

Employees working in a polluted atmosphere use respirators for health preservation. If the air in the workplace is polluted with noxious gases, but contains a lot of oxygen they often use air-purifying respirators (APR). These respirators provide employees breathable air due to the cleaning of contaminated ambient air with gas canisters or cartridges. (Сanisters and cartridges are named "cartridges" in this text late - for brevity). There are cartridges of different types, and they must be chosen correctly, and replaced in time.

Capture noxious gases may be accomplished by the sorbents. These materials (activated carbon, aluminium oxide etc.) have a large specific surface area and can absorb gases. Typically, such sorbents used in the form of granules, and cartridge case is filled with them. Contaminated air travels through the bed of sorbent granules in the cartridge, and movable harmful gas molecules collide with the surface of the sorbent, and remain therein. The sorbent is saturated the molecules caught, and gradually loses its ability to capture the gases. So, contaminated air can pass through the saturated sorbent to the layers of fresh sorbent. The concentration of harmful substances in the purified air after prolonged use of the cartridge increases, and may exceed the Permissible Exposure Limit PEL. Therefore, the service life of the cartridges is limited. The bond strength between the captured molecule and sorbent has a small, and the molecule is able to separate from the sorbent and get into the air again. The ability of the sorbent to capture the gases depends on: the properties of the gases and their concentrations, the air temperature, the air relative humidity, the rate of air consumed by the employee, and many other factors. Activated carbon can be saturated with chemicals that make more stronger ties with molecules of trapped gases - to improve the capture of a number of harmful gases. The saturation of the activated carbon with iodine - improves the capture of mercury; saturation of metal salts - improves the capture of ammonia; saturation metal oxides - improves capture acid gases.

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Wikipedia