The M40 Field Protective Mask is one of various gas masks used by the military of the United States

Military of the United States

The United States Armed Forces are the military forces of the United States. They consist of the Army, Navy, Marine Corps, Air Force, and Coast Guard.The United States has a strong tradition of civilian control of the military...

 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

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

.

Characteristics

The M40 Field Protective mask features 3 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

Blood agent

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

 attacks.

The M40 comes with a drinking system that allows the user to drink water when 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.

History

The M40 was the result of a program in the 1980s to develop a successor to the M17-series

M17 gas mask

The M17 gas mask is a series of gas masks that were designed and produced in 1959 to provide protection from all types of known chemical and biological agents present. The M-17 was issued to troops in the Vietnam war, and was standard issue for the U.S Army until it was replaced by the M-40 in the...

 protective masks which had been in service with the US armed forces from the 1960s. The M40 was to be a return to conventional gas 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 US Army in the mid-1990s, with another new design, the MCU-2/P similarly replacing older masks in service with the Air Force. However, both masks suffered from the inadequate protective capabilities of their facepiece, which was of a silicone rubber susceptible to corrosion from blister agent

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 affected...

s. Thus, the masks were effectively ill-suited for protecting against much more than riot control agents, and a butyl rubber '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 crews, who have to connect their masks to and draw air from their vehicle's own filtration system.

The M40 field protective mask, along with the older M17 mask, are currently being replaced by the M50 Joint Service General Purpose Mask

M50 Joint Service General Purpose Mask

The M50 Joint Service General Purpose Mask is the United States armed forces gas mask, which began service in December 2009, replacing the M40 Field Protective Mask.-Description:...

.