The following intelligence report on carbon monoxide fumes in tanks and armored vehicles during WWII was originally published in Tactical and Technical Trends, No. 9, Oct. 8, 1942. [DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]

INVESTIGATION OF FUMES IN ARMORED VEHICLES It has been recognized for some time that tank crews face a danger from collection, within the tank, of carbon monoxide fumes caused by the firing of tanks' guns with the hatches closed. The Canadians are now conducting tests in a Ram II tank with an auxiliary ventilation system which it is hoped will completely eliminate this hazard. The ventilating device consists of an exhaust fan installed under the ventilator in the roof of the main turret, and connected by a duct leading to a hood or intake attached to the ceiling of the turret at a point over the breech of the six-pounder gun. The exhaust fan is of the electrolux type and operated by a high-speed 24-volt motor. The most efficient design for the fan and motor was selected after various tests. The intake is located at a point in the sponge-rubber ring near the main turret hatch, over the recoil mechanism. The smoke is therefore exhausted from the vicinity of the commander's position, where repeated tests have shown that the gases tend to collect in a pocket under the cover plates when the tank is closed up completely. The above auxiliary ventilation system was recently tested under battle conditions. During the firing tests, the hatches were completely closed. The ammunition used was service-type 6-pounder AP, with a full charge of nitro-cellulose propellant. As a result of the tests it was concluded that the ventilating apparatus completely corrected the previously dangerous condition resulting from firing with hatches closed. The highest average of concentration of carbon monoxide gas during these tests was 0.09 percent, whereas in earlier trials of other ventilating devices the average concentration had reached 0.15 percent, or over, in every test. Furthermore, in the previous tests the tank could not be kept fully closed throughout the duration of the trials, whereas in the present case there was no appreciable discomfort experienced in keeping the tank closed up until the average concentration of carbon monoxide had dropped substantially to zero.

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