A respirator cartridge or gas mask canister is a type of filter that removes gases, volatile organic compounds (VOCs), and other vapors from the air through adsorption, absorption, or chemisorption.

Workplace air that is polluted with fine particulate matter or noxious gases but that contains enough oxygen (in the US, this is ruled to be a concentration above 19.5%; in the Russian Federation, above 18%[citation needed]), can be rendered safe via air-purifying respirators.

This is a form of activated carbon saturated with copper, zinc, silver, and molybdenum compounds, as well as with triethylenediamine (TEDA).

[ND2] In the European Union (EU) and the Russian Federation (RF),[10][11][12][13][14] manufacturers can certify cartridges intended for cleaning the air of various gaseous contaminants.

Service lives of all types of cartridges are limited, therefore, the employer is obliged to replace them in a timely manner.

[16] These signs (known in the US as "warning properties" - p. 28[16]) indicate that one must leave the polluted workplace area, and replace the cartridge with a new one.

The advantages of this method – if harmful gases have warning properties at concentrations less than 1 PEL, the replacement will be produced on time (in most cases, at least); the application of this method does not require the use of special cartridges (more expensive) and accessories; replacement happens when one needs to do it – after the sorbent saturation, and without any calculations; the sorption capacity of the cartridges is fully expired (which reduces costs for respiratory protection).

So, if one uses warning properties to replace cartridges, this may lead to breathing air with an excess harmful gas concentration in some cases.

[22] A study[23] showed that on average 95% of a group of people have an individual threshold of olfactory sensitivity in the range of from 1/16 to 16 from the mean.

Prolonged exposure to harmful gases (for example, hydrogen sulfide) at low concentrations can create olfactory fatigue which reduces sensitivity.

In a group of workers, the average styrene odor threshold increased by an order of magnitude due to adaptation.

[24] This was the reason for the ban to use this method of cartridge replacement in the US since 1996 (the Occupational Safety and Health Administration OSHA standard).

For example, the book[25] describes gas cartridges (model "СО"), which were replaced after a weight gain (relative to initial) of 50 grams.

The documents[27][28] describe a non-destructive way to determine the remaining service life of new and used gas cartridges.

The spectral method is based on determining the presence of harmful substances in the cartridge by sampling, with subsequent analysis on a special device (стилоскоп - on Russian).

If the air is contaminated with the most toxic substances, the book recommends to limit the further duration of cartridge use, and it recommended to apply the spectral method (arsine and phosphine, phosgene, fluorine, organochloride, organometallic compounds), and microchemical methods (hydrogen cyanide, cyanogens).

[31] If the company has a laboratory with the right equipment, specialists can skip the contaminated air through the cartridge and determine the degree of cleaning needed.

[citation needed] Research to determine whether it is possible to calculate the service life of respirator cartridges (if one know the conditions of their use) have been conducted in developed countries since the 1970s.

[citation needed] The world's leading respirator manufacturers offered customers computer programs for calculating the service life already in the year 2000.

Wood developed a mathematical model and software that now allows one to calculate the service life of any cartridges with known properties.

In addition, calculation accuracy is reduced under very high relative humidity, because the mathematical model does not take into account some of the physical effects in such cases.

Therefore, respirator manufacturers fear commercial failure when selling new unusual products, although they continue to carry out research and development work in this area.

Active end-of-service-life indicators: Examination of respirator use in the US showed that over 200,000 workers may be exposed to excessive harmful gases due to late replacement of cartridges.

[47] Since it is not always possible to replace cartridges in a timely manner through the use of their odor ets,[clarification needed] OSHA has banned the use of this method.

The employer is obliged to use only two ways to replace cartridges:[63] on schedule, and by using ESLI (because only these methods provide reliable preservation of workers' health).

[64] On the other hand, the state requires manufacturers to provide the consumer with all necessary information about cartridges to allow one to make a schedule for their timely replacement.

Similar requirements exist in the standard on occupational safety, governing selection and application of RPD in EU.

So, if the period of continuous service life of the cartridge (calculated by the program - see above) exceeds eight hours (see tables 4 and 5), the legislation may limit their use to one shift.

[75] The study[70] also showed that cartridges can be effectively regenerated after exposure to methyl bromide (when they are blown with hot air 100 to 110 °C, flow rate 20 L/min, duration about 60 minutes).

However, in the mass use of gas masks under different conditions it is impossible to control the accuracy and correctness such regeneration of respirators' cartridges.