Improvements in the polivalent filters of war for the chemical defense (Machine-translation by Google Translate, not legally binding)

摘要

Improvements in polyvalent war filters for chemical defense, characterized in that they only penetrate the aspirated air, the expired air being expelled directly into the atmosphere, for which the piece of the mask in which the filter is inserted is equipped of a system of suitable valves. (Machine-translation by Google Translate, not legally binding)