Gas masks and filters are used to protect the body from the harmful effects of chemicals and biology. Many chemicals such as chlorine, hydrocyanic acid, phosgene, mustard gas and others were used during World War I. They caused a number of casualties among the Allied troops and required protective masks.
Since then, gas masks have evolved to protect against all known types of chemical and biological agents. The best-rated military grade gas mask use a variety of techniques to protect the wearer. But the usual components like face masks, hoods, eyepieces and filters are present in almost all masks.
The most basic masks use filter techniques. Pollutants usually have a larger particle size than oxygen and can be trapped using fine mesh. Other methods use the absorbent properties of certain chemicals, such as activated charcoal, to control pollutants. Such masks have limited use because they absorb only a small amount of chemicals.
Modern masks use chemical neutralization methods. These masks contain chemical filters that neutralize harmful chemicals in the air. Some also have drinking water lines, communication systems, and hibernation equipment to prevent sweating in cold weather.
Chemical and biological agents have been used in the past and are being used again. The military is working with other researchers to improve the quality of existing masks and develop new protection systems. This will help them work in problem areas without risking their lives.