Generally gas masks are constructed from a thick non-permeable rubberised plastic, some having an in-built protective hood covering the head. The rubberised plastic is designed to form an airtight seal against the skin. For this reason facial hair heightens the risk of a 'bad seal' and should be avoided in an NBC environment (this is the primary reason that the Navy changed it's regulations and outlawed beards several years ago).
Gas masks use replaceable charcoal filters that filter liquid, aerosol and vapour toxins from contaminated air. Gas mask filters have a limited lifespan. They must be replaced if they are damaged, exposed to water/moisture, after a set period of exposure in a contaminated environment, after prolonged usage in a non-contaminated environment, or if their "shelf life" has expired.
Overgarment. The charcoal impregnated overgarment are semi-permeable and must be worn over normal combat clothing. The overgarment fabric has an impregnated charcoal lining that works in exactly the same way as a gas masks respirator filter, removing toxins and contaminants.
The semi-permeable fabric allows perspiration to escape (sort of). The overgarment offers protection against toxins and chemical agents in liquid droplets, vapour and aerosol form. Because the fabric is semi-permeable it cannot protect the wearer against liquids, and wet or saturated suits (either by precipitation, chemical agent or from the military member's own perspiration) are compromised and must be replaced.
The overgarments are designed to have a limited lifespan, and must be replaced after a set exposure or wearing time.
Overboots and Gloves. NBC protective overboots and gloves are constructed from thick impermeable rubberised plastic and are worn over normal combat boots and cotton liner gloves. Glove thickness can be varied for operation requirements where dexterity is at a premium.
Unfortunately, while the U.S. Military chemical-defense ensemble provides a high degree of protection, it can also reduce work and combat effectiveness by hampering vision, hearing, and dexterity. It can cause mental stress and heat exhaustion during heavy workloads in warm temperatures. That's where the Military MOPP Levels come into play.
By now, almost everyone who watches TV has heard the term "MOPP" when the news media talks about the potential chemical threat faced by members of our military. MOPP stands for "Mission-Oriented Protective Postures." MOPP levels allow commanders to escalate their protective postures based on the threat of imminent attack and accomplish operations by balancing mission continuation and force survivability. Because MOPP levels are standardized and easily understood, commanders can change protective postures without long explanations. Commanders can raise or lower protection through six levels, MOPP level 0 through MOPP level Alpha.
