A Guide To Choosing The Best Gas Mask Filters
Gas masks and respirators aren’t just generic preparation investments. As we recently covered in our Ultimate Gas Mask Guide, protective filtration masks can be life-savers in events like building fires and wildfires, and when dealing with contamination from natural and man-made disasters like earthquakes, volcanoes, or a nuclear reactor incident.
In an era of ever-increasing social strife, a gas mask can protect you from tear gas and pepper spray during riots and crowd control incidents.
But your mask is only as good as the filters you choose, so we’re going to cover the best 40mm gas mask filters.
Filter Factors to Consider
Color Codes and Ratings Explained
Gas mask filters are rated for protection against different particles and contaminants. Depending on what situation you’re prepping for, you’ll need to review the alphanumeric and color-coded ratings provided by the filter in question:
Color Code Examples
If we take the Mestel 40mm Filter from the list below, we find its filter ratings stamped on the side: “A2B2E2K2P3”. Reference the chart above to follow along: This code means the filter provides protection against gases and vapors with a boiling point greater than 65 degrees (C), inorganic gases and vapors, sulphur dioxide and hydrogen chloride, ammonia and organic ammonia derivatives, and radioactive particles. Speaking of numbers, the “2” or “3” present next to each letter code indicates what class of filtration is provided:
- Class 1 filters 1,000 parts per million (PPM)
- Class 2 filters up to 5,000 PPM
- Class 3 filters up to 10,000 PM
Other acronyms will indicate what kinds of agents your filter will block. For example, a filter described with an “NBC” rating means it protects against nuclear, biological, and chemical agents. A filter rated with a “CBA-RCA” rating means it protects against chemical, biological, and riot-control agents, but not nuclear.
Filter Threads and Fitment
There is some standardization in the threads and fittings used to pair filters with their respirators and gas masks. The most common threading you’ll find is the 40mm NATO Standard (Rd 40 x 1/7”), and this is typical for most filters on the market. Other threads will usually be specific to a corresponding respirator or mask model (like 40mm Soviet filters, which may use left-hand threads).
All gas mask filters have a shelf life. Most provide a shelf life of five to ten years, though high-end models can last for up to 25 years or more (with proper storage). When shopping for filters, never buy one that’s been unsealed. The media inside the filter must remain isolated from the environment, or it may absorb particles and contaminants in the air over time, diminishing its effectiveness.
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The Best Gas Mask Filters Compared
#1: Mestel 40mm NATO NBC/CBRN Gas Mask Filter
The best “catch-all” filter for all agents.
The Mestel 40mm Filter is one of the most popular and reliable gas mask cartridges on the market today. It’s rated to work all 40mm threads and masks, it provides active protection against chemical, biological, radiological, and nuclear agents. What’s more, it’s rated for crowd control chemicals, including CN, CS, and OC gas, pepper spray, and mace.
- Protection against virtually all known biological and chemical agents
- Protection against airborne bacteria, viruses, spores, and fungus
- EN P3 Certified with CLASS 3 Rating for nuclear/radiological particles
- Excellent protection against Sarin gas and DMMP
- Five-year shelf life, active filtration up to 24 hours
#2: MIRA NBC-77 Multi-Gas 40mm Cartridge (NBC/CBRN)
The most protective filter with the longest shelf-life.
The MIRA 40mm Filter is another top choice for its ability to filter most agents, including all NBC and CBRN agents, while affording users a solid 20-year shelf life. Uniquely, this filter includes a CBRN reactor, meaning the filter itself is capable of neutralizing particles that create harmful radiation, like iodine. This is a wonderful feature considering radioactive particles can still penetrate the skin and orifices if a user is exposed to such particles in the open environment (even if a mask is worn).
- Provides 20-year shelf life
- Compatible with all 40mm NATO respirators
- Rated to filter all known CBRN agents
- CBRN reactor neutralizes radioisotopes
- Constructed of high-impact plastic
If you are just looking for virus or bacteria protection (for diseases like COVID-19) then look at their ParticleMax P3 Virus Filter - 6 Pack.
Mira also offers two other interesting choices: the VK-450 Smoke / Carbon Monoxide Filter works not only NBC but smoke and carbon monoxide as well, at $89.95 a piece, and the affordable DotPro 320 40mm Gas Mask Filter offers full Spectrum protection from NBC/ABEK threats for only $39.95 each.
#3: Israeli Defense Forces M15 40mm Gas Mask Filter
The most affordable 40mm NBC filter.
We typically recommend against investing in military-surplus gas masks. Many are not capable of providing a proper seal around the face, and their filters are often expired (some older filters may include harmful asbestos, too). With that said, the Israeli Defense Forces’ new-stock, surplus 40mm filter is wonderful: It’s incredibly affordable, it provides complete NBC protection, and its threads are NATO-standard. Originally designed for the M15 mask (which we don’t recommend using), it’s compatible with nearly all masks. The big kicker is shelf life: Sealed units will last for up to 25 years, and they’re readily available as new stock.
- Manufactured date of 2017
- Sealed shelf life of up to 25 years
- Compatible with all 40mm NATO threads
- IDF specifications (meets U.S. Army C2 filter requirements)
#4: Avon XM50/M50 CBRN & NBC Filter
Double filtration for all agents, viruses, particles, and chemicals.
The Avon M50 filter set is perhaps the most “rugged” or capable filter set available. While it only provides a shelf life of up to five years, the M50 filter provides complete protection against virtually all known agents of any type for up to 24 hours. It’s 100% CBRN- and NBC-rated and protects against all nerve, blister, blood, and riot control agents.
- Up to 24 hours of protection against CB and radioactive agents
- Twin filter system provides low profile and extra protection
- Double filter set provides higher flow rate, easier breathing
- Provides additional protection against viruses and bacteria
- Up to five-year shelf life
#5: Drager 40mm CBRN Gas Mask Filter
A rugged, affordable filter with a wide range of protection.
Drager’s a well-known name in the respirator field and their 40mm CBRN filter is no exception. It provides excellent protection against most gases, vapors and particles (A2B2E2K2P3) and features a very well-built and rugged aluminum housing. Standard 40mm NATO threads make it compatible with nearly all masks. Shelf life is rated at six years for gas and combination filters, and twelve years for particle filtration. It’s one of the most affordable filters that provide this level of protection.
- Six- and twelve-year shelf life
- Class 3 (10k PPM) particle filtration
- Wide range of class 2 protection
- Durable aluminum housing
- CE-approved, SAI Global-approved
Author Bio: Travis Noonan is a military veteran and prepper who writes for Bug Out Bag Builder. When he’s not writing, he’s busy finding the best tactical gloves, range bags, shooting glasses, and active hearing protection for shooters and preppers at RangeOften.com.