The Armored-Vehicle Protective-Mask 3 History - development of gas mask for use by military-tank personnel

CML Army Chemical Review, July, 2000 by Robert D. Walk

In addition to the modern use of chemical agents in war, armored vehicles (tanks) were used first in World War I. The crewmen who operated these armored vehicles required protection. Initially, these soldiers were masked with the same mask as the infantry, but proper use of the sights required the use of special masks. Since operating in a tank is like operating in a confined space, air had to be supplied. After extensive research, air suppliers or "collective protectors" were developed and issued to tankers. They required special masks or adapters for the standard mask to work properly. This is their story.

Early Efforts

The Chemical Warfare Service developed a gas mask for use with optical instruments for the U.S. Navy in the 1920s. This was the experimental Navy Diaphragm Optical (NDO) Mark I. The Army recognized the need for the same capability and adopted the NDO as its optical gas mask, MI. This mask had a filter mounted behind the head and a diaphragm to allow better speech transmission. Although the theory was great, it was not successful for Army use. The optical lenses were good, but were small, which considerably narrowed the soldier's field of view. The filter mounted behind the head caused problems in the cramped confines of a tank turret. It was still on the armored-battalion equipment lists in 1943, but it was not truly acceptable to the armored force.

The M2 optical gas mask replaced the MI optical gas mask. The M2, sort of an NDO and lightweight gas-mask hybrid, had an NDO derivative facepiece with a lightweight gas-mask hose and M10 filter. This mask was produced in World War II with an M8 outlet valve and during the Korean conflict with a C15 outlet valve. The M2 optical gas mask provided improvements over the standard MI optical mask by mounting the filter on the soldier's side instead of behind the head. This improved the soldier's ability to maneuver inside the tank, but the soldier still suffered reduced visibility inside the tank turret. Development of a proper armored-vehicle crewman's mask continued, but further work included a centralized filter system to provide air for the vehicle crew.

Collective Protection

Much consideration was given to protecting the soldiers manning the tanks. Soldiers operating in the cramped, stuffy confines of a tank could use a blast of fresh air across the face. A formal requirement in 1943 established CWS D4.1-11, Collective Protectors for Tanks. Two areas of research were initiated--positive pressure for a sealed-crew compartment (fully overpressurized)--and supplied air to ventilated facepieces for already existing tanks. The first (overpressure) system was installed during manufacture, while the second (ventilated facepiece) system was a retrofit for current vehicles.

Beginning with the T23 tank project, the idea of an incorporated collective protector was included in the basic tank-design requirements. Because it was difficult to seal tanks completely, particularly during firing the main gun, the ventilated-facepiece program was more successful than the overpressurized system. It is interesting to note that captured German research revealed a planned overpressure system for their Tiger and Panther tanks. The American ventilated-facepiece-system program resulted in the E21-series collective protector.

The E21, designed by engineers at the Massachusetts Institute of Technology, used the concept of the ventilated facepiece for the soldier. A central filter unit provided air to two to three permanently connected facepieces. Efficient and effective, it provided overpressurizedfiltered air to the soldier's facepieces. Each mask had no outlet valve, so the air was constantly flowing around the periphery of the mask. When the soldier inhaled, the mask, made of thin rubber, instantly sealed against his/her face. The facepieces were not detachable, so the soldiers carried standard masks with them at all times so they could quickly dismount from the tank while protected.

Units that were produced included the E21R2 with one filter unit that protected one to three soldiers; the E21R3 with two filter units that protected two to six soldiers; and the E21R4, which was an E21R3 with a different filter unit. An M4A3 Sherman tank required two E21R2 units or one E21R3 or E21R4 unit. In 1945, the E21R2 unit was considered satisfactory for use in the Pacific for the impending invasion of Japan, but the Army ground forces did not adopt it because of the lack of detachable masks. The mask was also deficient when used with optical devices.

A limited procurement (1,000 sets) of the E21-protector series was authorized in World War II. One hundred-fifty E2lR2s and 350 E21R3s were produced. Electrolux [TM] manufactured all units in 24 volt, while a 12-volt conversion set was authorized, but cancelled after VJ-day.

After the war, research and development continued. Recognizing the need for adequate protection for tank crews, work continued and the specifications changed to include a removable mask for use by the tank crew outside of the tank. Postwar research resulted in the E25-series protector with two filter units and six masks. The blower used the tank's 24-volt system and delivered 3 1/2 cubic feet per minute of filtered air to each tank crewman. Each mask could be easily disconnected by the operator and used outside of the tank, eliminating the need for the soldier to carry a standard service mask.