The M40 field protective mask was one of various protective masks used by the

United States Armed Forces The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is ...

and its allies to protect from field concentrations of chemical and biological agents, along with radiological fallout particles. It is not effective in an oxygen deficient environment or against

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogeno ...

History

The M40 was the result of a program in the 1980s to develop a successor to the M17-series protective masks which had been in service with the US armed forces since 1959. The M40 was to be a return to conventional protective mask design with an external side-mounted filter canister, rather than the internal cheek filters of the M17, which were awkward to change, especially in a contaminated environment. The final prototype, the XM40, was approved for service and then designated the M40. The M40 was phased into service with the U.S. Army and

Marine Corps Marines, or naval infantry, are typically a military force trained to operate in littoral zones in support of naval operations. Historically, tasks undertaken by marines have included helping maintain discipline and order aboard the ship (refle ...

in the mid-1990s, with another new design, the MCU-2/P also replacing the older M17 in service with the

U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sign ...

and

Navy A navy, naval force, or maritime force is the branch of a nation's armed forces principally designated for naval and amphibious warfare; namely, lake-borne, riverine, littoral, or ocean-borne combat operations and related functions. It include ...

. However, both masks suffered from the inadequate protective capabilities of their face pieces, which was of a silicone rubber susceptible to corrosion from

blister agent A blister agent (or vesicant), is a chemical compound that causes severe skin, eye and mucosal pain and irritation. They are named for their ability to cause severe chemical burns, resulting in painful water blisters on the bodies of those affec ...

s. Thus, the masks were effectively ill-suited for protecting against much more than

riot control agent Riot control measures are used by law enforcement, military, paramilitary or security forces to control, disperse, and arrest people who are involved in a riot, unlawful demonstration or unlawful protest. If a riot is spontaneous and irr ...

s, and a

butyl rubber Butyl rubber, sometimes just called "butyl", is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as "PIB" or polyisobutene, (C4H8)n, is the ...

'second skin' had to be quickly issued for fitting over and reinforcing the M40 facepiece to make it effective in its intended role. The M42 series masks are a variant of this mask with alterations that make it better suited for use by

armored vehicle Military vehicles are commonly armoured (or armored; see spelling differences) to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighti ...

crews, who have to connect their masks to and draw air from their vehicle's own filtration system. The M40 field protective mask is currently being replaced by the M50 joint service general purpose mask. On September 2, 2017, the

Philippine Marine Corps The Philippine Marine Corps (PMC) ( fil, Hukbong Kawal Pandagat ng Pilipinas) is the marine corps of the Philippines, a naval infantry force under the command of the Philippine Navy. The PMC conducts amphibious, expeditionary, and special ...

received 1,000 M40 gas masks and C2 filters through the U.S. Embassy's Mutual Logistics Support Agreement program.

Design

The M40 field protective mask features three voicemitters, one on either the right or left side, and one in front. A voicecom adapter may be placed over the front voicemitter to amplify the user's voice. The mask can be adjusted in the field to accept the filtering canister on either side, so that a weapon may be shouldered. Right-handed shooters will normally locate the canister on the left side of the mask and vice versa. The C2 canister on the M40 mask can protect the user from up to 15 nerve, choking, and blister agent attacks, and two

blood agent A blood agent is a toxic chemical agent that affects the body by being absorbed into the blood. Blood agents are fast-acting, potentially lethal poisons that typically manifest at room temperature as volatile colorless gases with a faint odor. T ...

attacks. The M40 comes with a drinking system that allows the user to drink water after donning the mask for long periods of time in a chemically contaminated environment. In order to use the drinking system the user must also have suitably equipped canteen lids or an adapter for other containers.

Users

Current

* : In service with the

Philippine Army The Philippine Army (PA) (Tagalog: ''Hukbong Katihan ng Pilipinas''; in literal English: ''Army of the Ground of the Philippines''; in literal Spanish: ''Ejército de la Tierra de la Filipinas'') is the main, oldest and largest branch of the A ...

and

, supplied from the Joint U.S. Military Assistance Group.

Former

* : Replaced by the M50 joint service general purpose mask in active service. Still used by U.S. Army Reserve and National Guard units and the U.S. Marine Corps Reserve as of 2021.Military.com: New Gas Mask on the Way
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References

{{commons category, M40 Field Protective Mask United States Marine Corps equipment Gas masks of the United States Military equipment introduced in the 1990s