Gasproof shelter

For use in the field, a collective protector should be portable on muiur transportation and should be furnished in at least two sizes—one purifying sufficiont air for small gasproof shelters in the fonvard part of the combat area, and one purifying sufficient air for larger shelters in the rear ureas of the combat zone. 

Field Artillery and Coast Artillery. Twenty percent of the annual allowance of subcalibre ammunition will be fired under conditions involving the wearing of the gas mask by all men employed in the battery, except these detachments which would normally operate in gasproof shelters. (F.M. 21-40, 21-45, 100-5, TM 3-205.)... 

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