Gas masks are widely used by the world armed forces. Although it is possible to design a filtering device that will neutralize almost all specific toxic substances in the air, it is not possible to combine in one mask protection against all toxic substances. A protective military grade gas mask is mated with a view to ward off chemicals that are considered most likely to use in the war.
The gas mask is effective only against a chemical war agent that is spread as a true and dangerous gas when breathing. Agents such as mustard gas that are dispersed in liquid form and attack the body through the skin surface necessitate the use of special protective clothing in addition to gas masks.
A gas mask is basically a breathing device designed to protect the wearer against harmful substances in the air. The typical gas mask consists of a tight-fitting facepiece that contains filters, an exhalation valve, and transparent eyepieces. It is held to the face by straps and can be worn in association with a protective hood.
The filter elements in the cheeks of the mask remove contaminants from the air that is drawn through the mask by the wearer’s inhaling. The filters, which can be replaced, clean the air but do not add oxygen to it (some masks are connected by a hose to a separate tank of oxygen). The most common filters employ fiber screens and chemical compounds such as charcoal to capture or chemically alter poisonous gases in the air.