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A gas mask is a mask worn on the face to protect the body from airborne pollutants and toxins. The mask may cover the eyes and other vulnerable soft tissues of the face, and will always form a sealed cover over the nose and mouth.
Toxins may be gaseous (for example the chlorine used in WWI), or particulate (such as many biological agents developed for weapons). Many gas masks include protection from both types of toxin. The advantage of a gas mask over other breathing devices is that it does not require the user to carry an air supply (as in the use of scuba gear). However, this means that the user is dependent on the air in the atmosphere, the very medium in which toxins may be present. Thus, the mask must remove the toxins, and relay cleaned air to the user.
There are three main ways of achieving this: filtration, absorption and adsorption, and reaction and exchange.
1 Filtration
This obviously lends itself to particulate toxins. A filter works by having holes that are smaller than the particles to be removed. As many pollutant molecules and particles are much bigger than air molecules (mostly O2 and N2) this works for many applications.
However, the smaller the gap through which the air has to pass, the greater the pressure that must be exerted to draw the air through. As the user's lungs provide this pressure there is a limit as to how small these passages may be. Thus to extract many gaseous toxins, other methods must be used.
2 Absorption and adsorption
Absorption is the process of being drawn into a (usually larger) body, or substrate, and adsorption is the process of deposition upon a surface. This can be used to remove both particulate and gaseous toxins. Although some form of reaction may take place, it is not necessary, the principle may work by attractive charges (for example if the target toxin is positively charged, use a negatively charged substrate). Examples of substrates include activated carbonAlternative meaning: Carbon (computing Carbon is a chemical element in the periodic table that has the symbol C and atomic number 6. An abundant nonmetallic, tetravalent element, carbon has several allotropic forms: diamonds (hardest known mineral). Bindi, and zeoliteZeolites are minerals that have a porous structure. There are about four dozen recognized naturally occurring zeolite minerals and as many or more synthetic varieties. They are basically hydrated alumino- silicate minerals with an "open" structure that cas. this effect can be very simple and highly effective, for example using a damp cloth to cover the mouth and nose whilst escaping a fire. Most of the harmful vapours and smokeFor the movie starring Harvey Keitel, see Smoke (movie); for the cigar aficionado magazine, see Smoke (magazine) Smoke is a suspension in air of small particles resulting from incomplete combustion of a fuel. It is commonly an unwanted by-product of fires will be dissolved in the waterDrinking water This article focuses on water as we experience it every day. The water (molecule) article describes water from a scientific and technical perspective. Water is an abundant substance on Earth. It exists in many forms, such as sea, rain, and on the cloth, giving you vital extra seconds to escape.
