Chemical-Biological Mask: Field M40

After experimentation with the XM30 Mask (adopted as the MCU-2/P), the M40 Gas Mask entered service in 1987 as the standard replacement for the M17 Field Protective Mask.

Marine breaks the seal of his M40A1 Field Protective Mask during Nuclear, Biological, Chemical (NBC) training at Marine Corps Air Station Cherry Point, NC, 25 August 2004
Marine breaks the seal of his M40A1 Field Protective Mask during Nuclear, Biological, Chemical (NBC) training at Marine Corps Air Station Cherry Point, NC, 25 August 2004.

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M40 Gas Mask

Marines assigned to 2nd Battalion, 25th Marines, performing a head shaking maneuver to ensure that their M40A1 Gas Masks are properly fitted during Nuclear, Biological, Chemical (NBC) training, Camp Fuji, Japan, 16 July 2004
Marines assigned to 2nd Battalion, 25th Marines, performing a head shaking maneuver to ensure that their M40A1 Gas Masks are properly fitted during Nuclear, Biological, Chemical (NBC) training, Camp Fuji, Japan, 16 July 2004.

Field Protective Mask, M40 provides respiratory, eye and face protection against chemical and biological agents, radioactive fallout particles, and battlefield contaminants. The M40 is the mask issued to dismounted soldiers. The closely related M42 Combat Vehicle Crewman Mask is used by soldiers mounted in vehicles. Ground forces of the U.S. Army and Marine Corps are the primary users of the M40 Gas Mask, with selective use by other services.

Pre-Planned Product Improvement (P3I) Programs developed the M40A1 (1992) and M40A2 configurations of the M40 Gas Mask. The improvements include a quick-doff hood, second skin, voice amplification (M7), revised nosecup, two new carriers, and improved vision correction.

M40 Gas Mask Description

The mask consists of a silicone rubber facepiece (made in small, medium, and large sizes) with an in-turned peripheral face seal, binocular rigid eye lens system and elastic head harness. Other features include front and side voice transmitters, a drinking tube that mates with the M1 canteen cap, clear and tinted inserts, and a filter canister with NATO standard threads. The combination of M40 mask features allows the mask to be worn continuously for 8 to 12 hours.

The face-mounted canister containing the gas and aerosol filter can be worn on either the left or the right cheek. It has capacity to withstand a maximum of 15 nerve, choking, and blister agent attacks. It will also withstand a maximum of two blood agent attacks. Biological agents do not degrade the filter. The technical description includes these parameters:

  • Protection probabilities:
    • 95% against 5,000 mg-min/m3
    • 75% against 20,000 mg-min/m3
    • 50% minimum probability of achieving no more than .002 percent penetration of Bacillus globigii.
  • Breathing resistance: not greater than 55mm of water at 85 liter/min

The M40 series of gas masks are manufactured by ILC Dover, Frederica, DE. The standard nomenclature and other information for the M40 series of Protective Gas Masks is tabulated below. NSN includes mask, carrier, filters, waterproof bag, eyelens outserts & hood.

  • Chemical-Biological Mask, Field, M40 or Protective Mask, M40
    • NSN 4240-01-258-0061 Small
    • NSN 4240-01-258-0062 Medium
    • NSN 4240-01-258-0063 Large
  • Chemical-Biological Mask: Field, M40A1
    • NSN 4240-01-370-3821 Small
    • NSN 4240-01-370-3822 Medium
    • NSN 4240-01-370-3823 Large
  • NATO standard external filter canister
    • NSN 4240-01-119-2315

Technical Manuals for the M40 series of gas masks include:

  • TM 3-4240-300-10-1 Operator's Manual for Chemical-Biological Mask: Field M40 (15 Jun 1988)
  • TM 3-4240-300-20&P Unit Maintenance Manual (Including Repair Parts and Special Tools List) For Chemical-Biological, Mask: Field M40 (30 Aug 1996)
  • TM 3-4240-339-10 Chemical-Biological Mask: Field, M40/M40A1 (1 Feb 1994)
  • TM 3-4240-346-10 Operator's Manual for Chemical-Biological Mask: Field, M40A1 (1 Aug 1998)

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