The M5-11-7 Assault Gas Mask was a modified version of the M3 lightweight service gas mask. The nomenclature "M5-11-7" referred to its components, the M5 faceplate, the M11 canister, and the M7 carrier bag.
M5-11-7 Combat Gas Mask, from TM 3-205, from the collection of Jeffery Smart, U.S. Army RDECOM Historian.
During World War II, starting in 1942, the Chemical Warfare Service (CWS) established a laboratory at the Massachusetts Institute of Technology (MIT -- Boston, MA) to assist in the development of improved gas masks. The field soldier wanted a lighter gas mask and this became a top priority. The MIT lab conducted a series of tests which pointed to the cheek-mounted canister as the best lightweight design, the basis of the M5-series mask.
U.S. Army Ranger wearing M5-11-7 Assault Gas Mask (in M7 carrier), Pointe du Hoc, Omaha Beach, 6 June 1944.
The neoprene M5 Assault Gas Mask was composed of a modified M3 gas mask facepiece with a cheek-mounted canister, eliminating the hose. During experimentation it was known as the E6 mask and E3 canister filter. Upon standardization, it became the M5 faceplate and M11 canister. The rubberized cotton duck fabric bag for this mask was designated the M7 carrier. The complete unit was known as the M5-11-7 Assault Gas Mask, later changed to the M5-11-7 Combat-Service Gas Mask.
Production of the M5-11-7 Assault Gas Mask began in 1944 but soon was halted due to problems in the field. In cold temperatures the neoprene became stiff or rigid making it impossible to achieve a good fit. The production process had difficulties with molding the neoprene and was finally stopped as the failure rate became too great.
About 500,000 of the M5 gas mask were issued during 1944 and they were popular when used under the right conditions. The M5 was the gas mask issued to the first waves of troops on D-Day (Operation Overlord) on 6 June 1944. The M7 carrier, the waterproof bag, was worn on the chests of soldiers arriving by landing craft or was strapped to the thigh of paratroopers. The air in the M7 carrier made the bag a float, credited with saving the lives of soldiers who were dropped into deep water.
With the failure of the M5 gas mask, the CWS needed a replacement. In 1945, the M8 Snout Mask appeared as an interim solution.