The M25 Tank Gas Mask, approved for use in 1962 and fielded in 1963, is essentially identical to the M14A2 Tank Mask but with the addition of a new microphone system, the M116G used with the AN/VRC-12-series radios. Almost immediately, the M25A1 was adopted with minor changes and improvements including eye-lens outserts for arctic use and better fit. The M25A1 was produced until 1988 and remained in use into the 1990s, ultimately replaced by the M42 Combat Vehicle Gas Mask.
The M25 tank gas mask as issued consists of a wide view, clear plastic lens embedded in a butyl rubber face blank, an integral microphone with cord and coupler plug, eyelens outserts, heavy cotton duck carrying case, anti-fog kit, and an olive drab hose with mounted filter canister. As issued, the M25 Tank Gas Mask, carrier, and accessories are sealed together in a single foil package. Only the prong-type of optical insert fits M25A1 gas mask
The M25 Tank Gas Mask and the M25A1 mask are visually almost identical. If both are available for comparison, the M25A1 will be seen to have a higher forehead tab. The Mask Chemical-Biological Tank ABC-M25 is almost identical to the Mask, Chemical-Biological Aircraft, ABC-M24 except for the microphone. Filter canisters for the M24 and M25 masks are interchangeable -- both use the M10A1 CB canister (NSN 4240-00-127-7186).
When the M25 mask is used in a vehicle, the canister snout attaches to a filter unit, such as the M13A1 gas-particulate filter unit (GPFU). The GPFU forces filtered temperature- controlled air to the facepiece. This increases protection while reducing heat stress in hot weather. When wearing the M25 mask for stand-alone protection, the wearer inhales air through the M10A1 canister at the end of the hose.
The carrier bag allows the M25 mask to be slung over a shoulder or carried around the waist for rapid access in the case of NBC attack. The top flap is closed with three LTD fasteners or with a velcro strip. The carrier bag has an opening at the lower side for the snout of the canister to protrude outside the bag, so it can be quickly hooked to the vehicle GPFU without removing it. The carrier bag is stamped with "US" and "Mask, Protective, Tank M25A1" plus the size (S, M, L).
Accessories 
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ABC M5 Hood: The standard protective hood for the M25 and M25A1 mask, has a similar fastener to the M6A2 used on the M17 series.
M3 Winterization Kit: To be used when the temperature fall below 20 degrees F (-7 C), contains:
- Insulating jacket: Worn over the chin of the facepiece and upper end of the hose to retain the wearer's body heat inside the facepiece.
- Winterization outsert: A clear, insulated outsert that snaps on two adjustable studs on the facepiece, used to prevent the delicate plastic lens from frosting over.
- M2 Antiglare Eyelens Outsert: Originally issued to the M24. Used to help protect the wearer from intense sunglare from the snow.
Regarding Contents of Filter Edit
The M14, M24, and M25 masks are issued with M10A1 canisters. It is possible earlier models may contain asbestos. As the M10A1 canister was issued with several masks, such as the M3 Lightweight Service during the Second World War. Later models from the 80s to early 90s appear to contain ASC Wheterlite Carbon, which also contains Chromium VI, as stated in the operator's manual. It also states they're completely safe, as long as it's not damaged. This manual in particular was published in 1988.
