Gas masks and filters are used to protect the body from the harmful effects of chemical and biological agents. Gas masks use different techniques to protect the user. But the common components like face piece, hood, eyepieces and filters are present in almost all masks. You can buy the best gas masks from army surplus stores.
The most basic mask uses the filtration technique. Pollutants generally have larger particles than oxygen and by using a fine mesh these can be kept out. The only drawback is that air supply is also restricted in this process. The other process uses the absorbing qualities of certain chemicals such as activated charcoal to control the harmful agents.
Such masks have limited use, as they are able to absorb only a few chemicals. The present day masks use the method of chemical neutralization. These masks contain chemical filters that neutralize the harmful chemicals present in the air. Some of these also have tubes for drinking water, communication systems and winterization kits to prevent fogging during cold weather conditions.
These masks provide adequate protection only to the face and internal organs. A protective body suit attached to the mask is a good option to counter the harmful effects of such chemicals.