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Old 12-04-2019, 03:14 PM
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Exclamation CBRN FAQ Series: How long do respirator / gas mask filters last?

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QUESTION:I just bought a respirator/gas mask. Are the filters any good? How long will the filter last if I need to use it?

Storage Life

Provided they are properly sealed, the filters are good until the expiration printed on the packaging. This may be 1 year, 5 years, 10 years or even longer. Beware of companies claiming 20+ year shelf-lives, especially if the filter isn’t vacuum sealed. If the filters are surplus filters without an expiration date or the filters are not sealed in the original manufacturer's air-tight container or packaging, regardless of what the seller claims, they should be treated as “expired”.

After the expiration date, or if they are opened for any reason, the filters should be discarded and replaced. Contrary to popular opinion, gas mask filters are not simply activated charcoal sandwiched by filter medium. These filters also contain catalytic materials that react with some chemical vapors to neutralize them. Those materials may be in a separate layer in the canister, or the activated charcoal may be impregnated with these catalysts. Once exposed to air, these materials degrade and lose their protective properties.

Service Life

How long a filter cartridge will last is a complex problem and if you’re looking for a short, definitive answer, I’m afraid there isn’t one. There are no “rules of thumb” for how long a layperson can use a respirator in an emergency setting. In the professional world, the service life of respirator cartridges/filters is based on the concentration of the agent being filtered. It is highly unlikely a layperson will have access to the necessary tools or information to make an accurate measurement or estimate of the concentration. If you’re unable to determine the concentration, there’s no way to determine how long the filter can be expected to provide adequate protection. This is the number one reason laypersons should only use gas masks and respirators for escape. It’s also why virtually every guide, standard, or manual recommends the use of SCBA when the agent or concentration is not known.

The NIOSH CBRN Respiratory Protection Handbook recommends that NIOSH approved APRs (Air Purifying Respirators) be used for no longer than 8 hours once exposure to chemical warfare agents has started. If the respirator is exposed to liquid droplets, that time drops to two (2) hours. Note, that this doesn’t mean a respirator filter will last the full 8 hours, or even the full 2 hours. These times are for APR or PAPR devices. SCBA is actually less (6 hours). As with other hazardous chemicals, how well and how long a filter performs against chemical warfare agents is based on the agent and the concentration of that agent. Under high concentrations, the agent will break through the filter medium much faster than the times referenced above. Since some threats are odorless/tasteless at dangerous concentrations or may otherwise damage the sense of smell, you cannot rely on your sense of smell to tell you when you need a new filter.

Particulate-only Environments

Fortunately, most of the CBRN equation is composed of particulate agents. CS (Tear Gas), radioactive fallout (radioactive vapors and gasses excepted) and biological agents are all classified as particulates. Using a particulate filter (N95, N99, R99, P100, etc) in these environments doesn’t degrade the filter in the manner that a chemical environment degrades a filter. The particulates become trapped on or in the filter medium. Because of this, particulate filters don’t have an established service life. Instead, it is recommended that “All filters should be replaced whenever they are damaged, soiled, or causing noticeably increased breathing resistance (e.g., causing discomfort to the wearer).” How long that takes depends on how much “dust” is in the air. Keep in mind that the filter will become “hazardous” as you use it, so use caution when removing your mask or changing cartridges to prevent self-contamination.

Final Thoughts and Opinions

Remember, respirators do not provide you with oxygen, and will not protect you from environments where the oxygen has been depleted or displaced by other gasses. Thanks to charliemeyer007 for reminding me of this important caveat to respirator use. Many filter cartridges also do not filter combustion gasses like carbon monoxide. These gasses require special catalytic agents which convert the CO into CO2.

As a lay person, if you’re facing a CBRN environment and are using a respirator for anything other than to escape to a safe/safer location, you’re wrong. Contrary to internet wisdom, a respirator doesn’t give you the ability to penetrate or stay in a hazardous area. Donning your chem gear and a mask to go out and scavenge, or otherwise explore or otherwise exploit locations that unprotected individuals can’t, is the stuff of Hollywood and video game fantasy. In reality, these actions can get you killed in a CBRN environment. Especially where chemical agents are involved.

References and Related Reading

NIOSH [2018] Chemical, Biological, Radiological, and Nuclear (CBRN) Respiratory Protection Handbook. Retrieved From:

US Department of the Army. [2018] Pamphlet 385–61 Safety Toxic Chemical Agent Safety Standards. Retrieved From:

NIOSH [2005] Interim Guidance on the Use of Chemical, Biological, Radiological and Nuclear (CBRN) Full Facepiece, Air-Purifying Respirators/Gas Masks Certified Under 42 CFR Part 84. Retrieved From:

NIOSH [1996] NIOSH Publication Number 96-101 Guide to the Selection and Use of Particulate Respirators. Retrieved From:

NRC [2001] Manual of Respiratory Protection Against Airborne Radioactive Material (NUREG/CR-0041, Revision 1). Retrieved From:

Last edited by CONELRAD; 12-04-2019 at 05:14 PM..
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