The M40 series Field Protective Masks were used by the US Army, US Marine corps, and selectively by the US Navy. [2]. The masks were developed and introduced as a replacement to the M17 series, in service since 1959.

Mask, Field Protective, Chemical-Biological, M40

Mask, Protective Field, M40. With Carrier, M40/M42 Mask, Hood, M40/M42 First Generation, Canister, Filter, C2, Outserts, Lens, Clear and Neutral Gray, Bag, Waterproofing, MI, Manual, Mask, Chemical-Biological, M40/M42, and Flash Cards, PMSC.

Background Edit

The M17 introduced a number of features absent on the M9, such as a voice diaphragm, and with the M17A1, a drinking system.

The M17 Series had a number of shortcomings, however:

  • The M17's M13 filters were difficult and time-consuming to change, and couldn't be replaced while wearing the mask.
  • The use of internal filters added bulk and weight to the mask
  • M17s could be quite uncomfortable. Surfaces in contact with the face weren't textured, and the mask was made from blended natural rubber, making it more rigid than previous masks.
  • M17s lacked a peripheral seal.

Experimental versions Edit

In the 1970s the Army experimented with two new masks, the XM29 and XM30 series. These masks, however had several problems with the panoramic eyepiece as well as the fact that the silicone rubber it was made of was vulnerable to blister agents, which degrade silicone. The Navy and Air Force decided to develop the design further and finalized it as the MCU-2/P.

Learning from their mistakes, the Army decided to start over. In 1984, the ILC Dover company came out with the first prototype of the mask - the XM40. It was a very loose design, but it helped pave the way towards the development of the M40. The initial prototype was heavily influenced by the M17A1/M17A2 masks, and featured a dimple under the voice diaphragm for clearing the mask, a feature dropped in later prototypes.

Later, another XM40 prototype was designed. It was similar to the first, but more rigid. There were complaints about bulk, and so the mask was developed further.

Around the late 1980s the XM40 was finalized as the M40 Field Protective Mask, but it did not enter service until after the Gulf War (in which the M17A2 was mainly used). It was mass-produced and mainstay issued from 1992 onwards.

The Mask Edit

It had two large, polygonal, binocular sight plexiglass eyepieces, which came with a seperate pair of ballistic lens "outserts", like its cousin, the M17, but these outserts also came in a neutral grey (tinted) version for protection against UV rays and flashbang grenades. It had a large voice diaphragm (same as on the MCU-2/P Series) which had threads on the inside to fit an M7 or MSA Voice Amplification Unit. The outlet valve had a drinking tube built into it, which wrapped around the outlet valve cover and fit in a pocket on the cover (again, simillar to the MCU Series).

Inside, the mask has a peripheral seal, and the chin cup has a slit to allow sweat to pass down to the exhale valve. The orinasal cup is the same type as on the MCU-2/P. It used a 40mm threaded C2 canister which could be switched out on either side with a secondary side voice diaphragm (used for telephone communication) to accommodate left and right-handed rifle users. 

The facepiece is made of olive-coloured silicone rubber, as in the XM40 Series. To provide protection from blister agents, the mask was issued with a special hood made of Butyl Rubber-coated Nylon and had a specially made sheet of Butyl Rubber, sewn into the hood, that covered the facepiece, protecting the silicone facepiece from the harmful effects of blister agents. The Butyl Rubber "second skin" fastened to the facepiece with velcro patches near the bottom of the exhale valve, where a part of the hood curled under that had the patches to fasten on.

M40 Field Protective Mask

The M40 Field Protective Mask in use.

The second skin wasn't sewn to the bottom of the hood, in order to pull the bottom of the hood over the outlet valve to maintain positive pressure in the hood. This feature and the fact that the second skin fastened with velcro, made the whole assembly prone to leaks, so an update was needed.

M40A1 Edit

In the mid-1990s, the M40 was updated and re-designated the M40A1. It had a new orinasal cup, made of a smoother olive silicone. The hood and second skin were replaced as well - The second skin was a separate piece of molded butyl rubber, that once put on the mask, was meant to stay there (aside from cleaning or replacing when broken).

This new second skin did not cover the parts of the mask where the head harness buckles were attached, and had a up-raised peak of rubber, similar to the British S10 Facepiece, all around the edge of the skin. This was meant to help hold the new M40A1/M42A1 "Quick Doff" Chemical


The M40 mask in a combat setting during Operation IRAQI FREEDOM,

M40A1 Drinking Device In Use

The M40A1 being used with the drinking device.

Hood in place and prevent it from slipping off the mask. On the top and bottom of the skin, and on top of the hood peak, there were rubber tabs (one on top, near forehead, one on bottom, near chin), which were intended to further hold the hood in place.

The mask also was issued with a new type of canister - the C2A1. It differed from the older C2 visibly by the color - C2's were metallic black, C2A1's were metallic green. The C2 was still used, but eventually began getting phased out, and was eventually used only for training.

M40A2 Edit

Later in the late 1990's, the M40A1's second skin was updated, they did away with the S10-style hood stop system, and just left a small ridge-like hood stop on the chin. The second skin was slightly thinner, and it covered more of the mask, it also had a neck flap as well.

Aside from the second skin, everything else, especially the mask, remained


the same, but the change in the second skin design was enough to change the nomenclature, and thus the M40A1 was re-designated the M40A2.

To the right A full M40A2 kit showing the M40A2 face piece clear outserts, M40A1/M40A2 chemical biological hood, 3rd model Butyl "second skin", Faceform, PMCS card, Paper manual, C2A1 canister and the m40 series carrier.

FR-M40 Edit

MSA and Scott Aviation and ILC Dover (who helped develop and produce the M40 early on), sold the M40 contract to the adhesive company, 3M. 3M began producing the M40 as the FR-M40, intended for civilian use, and marked (NOT GOVERNMENT PROPERTY). Aside from this marking, the mask is identical to the M40A2.

Replacement by M50 Edit

From 2009 onwards, the M50 Joint Service General Purpose Mask started replacing the M40 Series, as well as the MCU-2/P

Accessories Edit

Ballistic Lens Outserts Edit

M40A2 Gas Mask With Laser Protective Lens Outserts

An M40A2 with the special Laser Protective Ballistic Lens Outserts. These are uncommon to find, and can be expensive when found.

These were made to protect the actual lenses themselves from damage, and could supposedly resist light shrapnel.There are three kinds;

  • Clear, just for protecting the lenses
  • Neutral gray, for protecting the eyes from sunlight and "flashbang" grenades
  • Laser protection, for protecting the eyes against laser light. These have a green tint, and are the rarest type of outserts.

M40/M42 "Quick Doff" Chemical Hood Edit

Issued with the M40A1 as a replacement for the older First Generation M40/M42 Hood, which had the second skin sewn in which was prone to leaks, the "quick doff" hood is a very simple chemical hood, made of nylon fabric, heavily rubberized with butyl rubber, with a large, circular, elasticated opening for the mask, two underarm straps made of the same material as the hood with metal adjustment buckles in the back and black plastic fastening clips in the front. The neck area has a built in elastic band, as to not need a confusing, time consuming drawstring cord and slider. The hood is very easy to use and could be used with a variety of gas masks, U.S. or not.

Optical Inserts Edit

A special pair of glasses that have special frames that fit around the inside the lenses, inside the
M40 Field Protective Masks In Use

M40 Field Protective Masks in use. Note the optical inserts in the mask of the soldier laying down.

mask. There are two types - a plastic frame type and a metal wire frame type.

MI Waterproofing BagEdit

Standard in most U.S. protective masks from the Vietnam War and onwards, the MI waterproofing bag is a large plastic bag used to keep the mask dry when fording rivers and streams, or whenever the mask may be exposed to water. The bag can degrade the protective qualities of the mask, and can have toxic effects when the bag contacts foodstuffs. The bag comes with a cardboard sleeve of rubber bands meant to close the bag. The bag is stored folded in a ziploc bag in one of the internal or possibly external pockets of the mask's carrier bag.

Preventative Maintainance Service Check (PMSC) Flash Cards Edit

Laminated flash cards on a metal ring that list problems and defects you need to check for on a certain basis for the M40 Series Field Protective Masks.

M40 To M42 Conversion Kit Edit

Unissued M40A1-M42A1

M40A2 with M42 Conversion Kit.

The M42 is the armored crew member's version of the M40 Field Protective Mask. It had a voice diaphragm with a built in microphone, for the tank's radio, and a long breathing tube (green hose fixed to the facepiece on the M42, then a threaded black hose to switch sides for left and right handed tankers on the M42A1 and M42A2). The C2 or C2A1 filter on the end of the hose had a special plastic casing (olive drab green plastic with metal coupling on the M42, then a black plastic case with black plastic coupling on the M42A1 and M42A2), which had a special coupling on the inlet port so that a hose from the tank's supplied air system could be attached to it. Every other aspect of the M42 series masks besides the hose, microphone, and filter casing and coupling are the same was their M40 counterparts. The M40A1 and M40A2 could be issued with a special conversion kit to field modify it into an M42A1 or M42A2 armored crew member's mask because making a seperate mask for a different purpose was costly. The kit came with the hose, casing with coupling and carrying straps, and a special clip on microphone that clips to the main voice diaphragm.

M40 Gas Mask With Toxicological Agent Protective (T.A.P.) Hood And Apron

An M40A1 with the M40 T.A.P. hood. It's remarkably similar to the M3 T.A.P. hood for the M9A1, with only minor differences. Worn here with the M2 T.A.P. Apron while inspecting drums of Distilled Mustard Gas for leaks.

T.A.P. Hood Edit

Like the M9A1 with M3 T.A.P. Hood, and the MCU-2/P with the HGU-65/P T.A.P. Hood, the M40 Series has had it's own T.A.P. Hood, meant for heavy decontamination, chemical stockpile inspection/handling, and other similar tasks. T.A.P. hoods for the M40 are very rare, and understandably expensive when found, not many photos exist of the M40 T.A.P. hood exist as well, information is rare, and as of now, the actual designation for the hood is unknown.

There also exists an early model designated XM3A1, it is vastly different in design compared to T.A.P. hoods seen on the M9A1 and later M40 variants. This version lacked filter sleeves, leaving the voice diaphragm and exhale valve exposed. As well as having what appears to be a type of second skin made from what is possibly an off white nylon coated butyl rubber. Possible design flaws were what have made the final variants for the M40 retain the filter sleeves and full enclosure to seal and partially inflate the T.A.P. hood via positive pressure, like that of M3 hoods used on the M9A1.


XM3A1 T.A.P. hood.

Foreign Variants And Export Edit

M3 Edit

Main article: M3 (Serbia)

The M3 is a Serbian copy of the M40. It's remarkably similar, however the voice diaphragm, filter, outlet valve and the size of the eyepieces (same shape as the M40) are slightly bigger than the M40. The drinking tube on the M3 is also very similar to the drinking tube used on the Canadian C4, because of the way it attaches under the left eyepiece and curls behind and under the filter inlet.

Jordanian/UAE Military Use Edit

While the mask is the same as the M40A1/A2, the key difference is the second skin, which is made of a tan butyl rubber. Very similar in design to the one sewn on the first generation chemical hood, (with the hood itself is not present on this version.) where it is secured around the exhale port and drinking tube via velcro. There is another version that is a direct copy of the M40A1's second skin made of a tan rubber in use with the UAE military.

US Navy useEdit

The M40 Series was not only used by the Army and Marine Corps, it's widely documented (mainly through photographs) that the U.S. Navy (especially the Seabees) adopted the M40 as well as either a replacement or a partner mask to the MCU-2/P Chemical Protective Mask.
U.S. Navy Members Of Explosive Ordnance Disposal Mobile Unit (EODMU) 11, Platoon 0-2, Take Their Positions On The Flight Deck Of The Aircraft Carrier USS Ronald Reagan During A Fast Roping Exercise

Members of the U.S. Navy Explosive Ordinance Disposal Mobile Unit 11 (EODMU 11) Wearing the M40A2 mask with the special PAPR blower filter system.

Another Navy unit that used the M40 was the Explosive Ordinance Disposal Mobile Unit 11 Team, but the mask was used with a special blower (PAPR) that had two C2 or C2A1 filter screwed on the front of it, the blower was worn on the belt or on the back, and the blower had an electric fan that sucked air through the filters and forced air through a long tube into the mask. The blower units are very rare, and are not usually found.

References Edit