Gas Mask Buyer’s Guide

RECOIL OFFGRID - - Front Page - By Bill Blow­ers

The his­tory of gas masks is long and var­ied, in hopes of match­ing the threat from var­i­ous dif­fer­ent types of agents. Early “masks” were just wet sponges cov­er­ing the user’s mouth and nose. As threats changed, so did the masks and the tech­nol­ogy be­hind them. Lots of peo­ple are fa­mil­iar with the M17 mil­i­tary gas mask, but like ev­ery­thing in life, fil­ters and com­po­si­tion have im­proved. To­day, the M17 is noth­ing more than a con­ver­sa­tion piece since the fil­ters con­tain chromium, which we now know to be a car­cino­gen.

The first ques­tion you should con­sider is whether you even need a gas mask. If the an­tic­i­pated threat is sim­ply riot con­trol agents (RCA), then any of the masks listed here will be fine. And de­pend­ing on how un­com­fort­able you want to be, so will a wet sponge. The penalty for ex­po­sure to RCAs is dis­com­fort for a brief pe­riod of time.

If it’s some­thing more ne­far­i­ous, like VX nerve agent, then a mask is only the first step since the agent can also be ab­sorbed through ex­posed skin. That type of threat re­quires full body pro­tec­tion and cov­er­age — but level A to D chem suits are a topic for another day.

In this ar­ti­cle, we’ll dis­cuss two types of threats: CBRN (chem­i­cal, bi­o­log­i­cal, ra­dio- log­i­cal, and nu­clear) and RCAs. Con­sid­er­ing the na­ture of these haz­ards, only full-face res­pi­ra­tors are con­sid­ered. These types of agents not only af­fect your breath­ing, but they’re par­tic­u­larly good at dis­rupt­ing your moist bits, like eyes, mouth, and nose. All of those ar­eas need to be cov­ered to be prop­erly pro­tected, hence the need for full­face pro­tec­tion.

Plenty of peo­ple lose their minds as soon as the “oc­to­pus” at­taches to their face. Hyper­ven­ti­lat­ing and feel­ings of claus­tro­pho­bia are fairly com­mon. So, if the face­hug­ger crea­tures from the Alien fran­chise re­ally freak you out, air-pu­ri­fy­ing res­pi­ra­tors (APRs) will take some get­ting used to. Draw­ing breath will be harder in an APR — you’re pulling air through a fairly dense fil­ter, so nor­mal breath­ing will be af­fected. Add in any phys­i­cal ac­tiv­ity, and it only gets worse.

It goes without say­ing that you should be checked by a doc­tor to de­ter­mine whether you’re healthy enough to wear a mask, how long you should wear it, and whether or not pro­longed use might have ad­verse health ef­fects. Most oc­cu­pa­tional health clin­ics can per­form this type of checkup since they rou­tinely do it for cops and oc­cu­pa­tions that re­quire res­pi­ra­tors.

Of course, if you’re faced with a sit­u­a­tion where a mask is truly needed, you’ll need to weigh the po­ten­tial health risk of wear­ing it ver­sus that of ex­po­sure. The gen­eral health checkup is still im­por­tant for train­ing in a mask though, so please don’t ne­glect it.

Se­lect­ing a full-face mask isn’t enough on its own — you’ll also need to con­sider its level of pro­tec­tion. In con­junc­tion with the type of fil­ter cho­sen, the mask ’s ma­te­ri­als are also im­por­tant. Butyl rub­ber (BR) and sil­i­cone are the most com­mon, with butyl rub­ber be­ing more re­sis­tant to UV and dif­fer­ent types of chem­i­cals. BR and sil­i­cone are most com­mon since they pro­vide a great seal­ing sur­face as well as re­sis­tance to a large va­ri­ety of agents.

Ide­ally, the mask you choose should accept fil­ters with a 40mm NATO thread. This will al­low you to choose from a va­ri­ety of NATO fil­ters. A NIOSH-rated (Na­tional In­sti­tute for Oc­cu­pa­tional Safety and Health) CBRN fil­ter will han­dle damn near ev­ery­thing. The MSA Ad­van­tage doesn’t have this fea­ture, so its value is di­min­ished as a re­sult. Fil­ter adapters are avail­able, but in­tro­duce an ad­di­tional point of po­ten­tial failure in a very im­por­tant sys­tem. Masks are cer­ti­fied, but only fil­ters are rated. To learn more about the ac­cred­i­ta­tion sys­tem you can visit­pi­ra­tors/dis­p_­part/de­fault.html.

The up­per por­tion of your mask should pro­vide clar­ity of vi­sion and keep pe­riph­eral vi­sion ob­struc­tions to a min­i­mum. It should be easy to don without a com­plex web­bing sys­tem, and lastly it should be com­fort­able to wear for pro­longed pe­ri­ods. A hy­dra­tion tube port is al­ways a wel­come fea­ture — in some hot­ter cli­mates and more stren­u­ous con­di­tions it should be con­sid­ered manda­tory. Re­mem­ber that you may not be able to take off the mask for sev­eral hours, and without a hy­dra­tion port, you won’t be able to drink any­thing dur­ing that time. A CamelBak adapter is read­ily avail­able for most masks with drink­ing tubes.

The ad­di­tion of voice am­pli­fiers and ra­dio ca­bles might also be manda­tory de­pend­ing on your task and pur­pose. And if you’re us­ing it fre­quently for po­lice or mil­i­tary op­er­a­tions, or if you’re re­ally com­mit­ted to mak­ing sure it can save your life, then you need to be clean shaven to en­sure the best seal. Sorry neck­beard dudes, but no amount of Vase­line smeared into your beard will give you the same seal as bare skin.


All of the masks eval­u­ated were size medium, and this au­thor tested all of them for “fit fac­tor” on an OHD Fit Test­ing Ma­chine. The OHD ma­chine is de­signed to test the over­all fit of the mask on an in­di­vid­ual user. The fil­ter is re­moved, and the ma­chine is hooked to the fil­ter port of any mask with 40mm threads. Once hooked up, the wearer goes through a se­ries of tests while hold­ing their breath. The ma­chine purges the air from the mask and cre­ates neg­a­tive pres­sure. Sen­sors de­ter­mine the over­all “fit” of the mask to the wearer. This takes the guess­ing game out of what size is best for you, and helps de­ter­mine the best size based on the shape of your face and head. The test procedure in­cludes stand­ing straight up, bend­ing over at the waist, vig­or­ous shak­ing of the head from left to right, and so forth.

You’re al­lowed to breathe in be­tween each test, but you must hold your breath for each event. The end re­sult is ei­ther a pass or fail, and the ma­chine will pro­vide a num­ber, or “fit fac­tor.” The higher the num­ber, the bet­ter the seal and fit of the mask to the user. If you don’t have ac­cess to a ma­chine, a neg­a­tive pres­sure test or the use of strongly scented sprays like Bitrex or ba­nana oil are good al­ter­na­tives. The lat­ter items should be avail­able through safety sup­ply dis­trib­u­tors that cater to in­dus­try pro­fes­sion­als. We’ll ex­plain neg­a­tive pres­sure test­ing in a bit, but for now let’s talk about the masks that were tested and eval­u­ated. A min­i­mum point value of 500 is re­quired to get a pass; there’s no max­i­mum num­ber that we’re aware of. The higher, the bet­ter.

Eval­u­a­tion Pro­ce­dures

With the ex­cep­tion of the Mes­tel mask, this au­thor has worn all of these masks into RCA en­vi­ron­ments for pro­longed pe­ri­ods of time dur­ing build­ing searches for crim­i­nals. Agent ex­po­sure was CS and OC — in other words, tear gas and pep­per spray. In most cases the agent was in both liq­uid and pow­der form, and usu­ally both types of agents were de­ployed on the lo­ca­tion. The Mes­tel mask was worn for a pe­riod of 90 min­utes to test for com­fort and weight, but due to the lack of a lo­ca­tion to de­ploy live agents, no agent ex­po­sure test was per­formed.

In ad­di­tion, we con­ducted pe­riph­eral vi­sion mea­sure­ments us­ing a stan­dard tape mea­sure. These mea­sure­ments were taken while stand­ing with head straight up and then while cast­ing eyes down to de­ter­mine how far for­ward we could see on the ground without tilt­ing the head. This is im­por­tant if you’re nav­i­gat­ing through a con­gested space, even more so in low light. We also took a mea­sure­ment look­ing straight down at the ground with head tilted for­ward. This sim­u­lates hav­ing to climb down some­thing or just look­ing for ob­struc­tions di­rectly at your feet.

Lastly, we mea­sured with head straight and then eyes moved hard left and right to de­ter­mine how much pe­riph­eral vi­sion was avail­able. These mea­sure­ments are in­di­cated be­low by straight, down­ward, and pe­riph­eral vi­sion loss, re­spec­tively. This was con­ducted us­ing a tape mea­sure with the base of the tape at the wearer’s feet. Zero inches would in­di­cate no loss of vi­sion and then ex­tends out from there. So the higher the num­ber, the fur­ther away the vis­i­ble point is.

Neg­a­tive Pres­sure Test­ing

While the OHD ma­chine pro­vides the best mea­sure­ment of fit, neg­a­tive pres­sure test­ing comes in sec­ond, fol­lowed by a squirt of Bitrex or ba­nana oil as men­tioned be­fore. A neg­a­tive pres­sure test is easy to per­form and can be done ev­ery time you put the mask on to en­sure you have a proper seal. If you think you’re al­ready ex­posed, hold your breath first. Don the mask, cover the ex­hale port, and breathe out force­fully. This will vent the con­tam­i­nated air that you just scooped onto your face. Im­me­di­ately cover the fil­ter in­hale port and at­tempt to breathe in. You shouldn’t get any air.

If you do get air, the mask isn’t se­cured prop­erly and is al­low­ing air to pass — or you didn’t com­pletely cover the fil­ter in­hale port. Re­po­si­tion and try again. Ad­just the head harness ac­cord­ingly. If you still sense agent, vent the mask again us­ing the procedure above, but don’t re­move the mask. Start at step two. If you’re sim­ply putting your mask on due to con­cern about pos­si­ble agents be­ing dis­sem­i­nated, there’s no need to hold your breath dur­ing the don­ning procedure.


If the eye­piece is fog­ging, it’s gen­er­ally an indi­ca­tor of a bad seal. Re­po­si­tion and go through the afore­men­tioned steps again. The mask is de­signed so that con­tam­i­nated air gets pulled through the fil­ter and cool air goes over the eye­piece to de-fog. The air is then drawn into the mouth/ nose piece, and you breathe the fil­tered air. When you ex­hale, di­aphragms in the nose piece are sealed. This forces the con­den­sa­tion and ex­haled air out of the ex­hale port. Breathe in and the di­aphragm on the ex­hale port is sealed.

Fil­ter Changes

If you’re in a chem­i­cal en­vi­ron­ment and need to con­duct a fil­ter change, take a deep breath and hold it. Un­screw the old fil­ter and screw on the new fil­ter without tak­ing a breath. Once the new fil­ter is seated, cover the ex­hale port and force­fully breathe out. If you in­ad­ver­tently breathe in with the fil­ter off, you’ll draw con­tam­i­nated air into the face piece. Once the new fil­ter is on, breathe nor­mally. It’s worth not­ing that this procedure is dif­fer­ent if you have an Air Boss LBM. The LBM is de­signed so that when the fil­ter is re­moved, a spring-loaded mech­a­nism seals the mask. If you at­tempt to breathe in, you won’t get air un­til the new fil­ter is seated. It goes without say­ing that you need to be able to con­duct a fil­ter change rapidly while wear­ing the mask in any con­di­tion.


Main­te­nance for all the masks is sim­ple. Re­move the fil­ter. Fil­ters can be ex­posed to rain and fog, but shouldn’t be submerged in wa­ter. Once a fil­ter is re­moved from its foil pack, it’s cer­ti­fied for 15 min­utes of use for the agents it’s de­signed to de­feat. For riot con­trol, you can re­use the same fil­ter over and over un­til you start to sense agent. Then re­place as nec­es­sary. For CBRN, you bet­ter have new ones in foil pack ready to go that aren’t ex­pired, per the date on the pack­age. If you don’t, use what you have, but you’ll be tak­ing a chance.

Once the fil­ter is re­moved, the whole mask can be dunked in warm soapy wa­ter and rinsed clean. Airdry and then use an ap­pro­pri­ate lens cloth on the eye­piece. If the mask is con­tam­i­nated with CBRN, you can’t just pop it of f and start clean­ing it. You need to go through an en­tire de­con process. For RCA, you can just clean it, but be care­ful about touch­ing your eyes, face, and other sen­si­tive ar­eas un­til your hands are thor­oughly washed as well.

For peace of mind, a cer­ti­fied CBRN fil­ter from a rep­utable man­u­fac­turer will work for both CBRN and RCA. They are fairly big, how­ever, so po­lice of­fi­cers may want a sep­a­rate RCA-only fil­ter as well as CBRN fil­ters stored in foil packs. This keeps the good ones ready and the smaller, usu­ally cheaper RCA fil­ters for most com­mon use.


This ar­ti­cle cov­ers just a small sam­pling of the many masks avail­able on the mar­ket. Most of them were cho­sen with the fight­ing man’s needs in mind, but many of those same needs are com­mon for the cit­i­zen. A base guide­line would in­clude: full face piece, 40mm thread com­pat­i­bil­ity, com­fort, and hy­dra­tion, with the cost fac­tor con­sid­ered af­ter all the oth­ers. Any­thing man­u­fac­tured prior to 2000 shouldn’t even be con­sid­ered for pur­chase, as tech­nol­ogy has ad­vanced way too far to accept any­thing else.

A mask is also only the first step in pro­tec­tion. Der­mal ex­po­sure is a con­cern for many CBRN agents, but that’s an en­tirely dif­fer­ent topic. A tall op­tic mount for your ri­fle al­lows for faster and eas­ier ac­qui­si­tion of sights, but a laser aim­ing de­vice is best when wear­ing a mask. If the mask man­u­fac­turer makes a lens cover, they’re highly rec­om­mended to keep the view­port clear. Most do, and some even of­fer smoke, yel­low, and laser safety lenses.

Lastly, if you’re con­sid­er­ing start­ing a riot or help­ing to main­tain a riot, and you’re read­ing this ar­ti­cle to thwart law en­force­ment at­tempts to main­tain the peace, then shame on you. No mask will pro­tect you against a bar­rage of less lethal mu­ni­tions or a pair of hand­cuffs.

OHD Fit Ma­chine

Fit­ment is just one part of the over­all puz­zle in de­ter­min­ing proper gas mask use. Have a doc­tor per­form a thor­ough phys­i­cal to en­sure you’re healthy enough to use one. Photo cour­tesy of Avon Pro­tec­tion.

Fil­ters with red cir­cles high­light­ing pro­tec­tion level, CBRN, and CS/ CN/P100. P100 means it’ll fil­ter par­tic­u­lates out of the air down to 1 mi­cron in size. The width of a hu­man hair is 75 mi­crons. CN is a riot agent that’s no longer used due to its high car­cino­gen fac­tor, but it’s still in­di­cated on fil­ters. OC is gen­er­ally never listed as an RCA, even though you wouldn’t want to in­hale it — OC is a de­riv­a­tive of hot pep­pers, thus it’s con­sid­ered a food prod­uct not an “agent.”

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