An overpressure protection system is one designed to protect an individual or group of individuals in a chemical, biological, radiological and nuclear (

CBRN Chemical, biological, radiological and nuclear defence (CBRN defence) are protective measures taken in situations in which chemical, biological, radiological or nuclear warfare (including terrorism) hazards may be present. CBRN defence consi ...

) environment. The two parts of the system are a safe area which as far as possible is

sealed Seal may refer to any of the following: Common uses * Pinniped, a diverse group of semi-aquatic marine mammals, many of which are commonly called seals, particularly: ** Earless seal, or "true seal" ** Fur seal * Seal (emblem), a device to impr ...

from possible contaminated air and an

air filtration A particulate air filter is a device composed of fibrous, or porous materials which removes solid particulates such as dust, pollen, mold, and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) may also ...

system which will filter out all possible toxins. Air pumps force clean air through the filters into the safe area such that the air pressure within the safe area will always be higher than that outside of the safe area. This pressure differential means that any flows of air will always be from the safe area to the outside, preventing the ingress of toxins. The safe area may be as small as a protective hood for an individual, to a full body

hazmat suit A hazmat suit (hazardous materials suit) is a piece of personal protective equipment that consists of an impermeable whole-body garment worn as protection against hazardous materials. Such suits are often combined with self-contained breathing ...

, to a

fallout shelter A fallout shelter is an enclosed space specially designated to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War. During ...

or warship. Most modern

armoured fighting vehicles An armoured fighting vehicle (AFV) is an armed combat vehicle protected by armour, generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked. Examples of AFVs are tanks, armoured cars ...

will have such a system with the safe area being the crew and passenger compartments, these systems being first adopted to protect against

poison gas Many gases have toxic properties, which are often assessed using the LC50 (median lethal dose) measure. In the United States, many of these gases have been assigned an NFPA 704 health rating of 4 (may be fatal) or 3 (may cause serious or perman ...

attack. On a larger scale an overpressure system may be designed into the structure of a building or mobile prefabricated military structures to provide

collective protection Collective protection is used for group protection of personnel in a nuclear, biological or chemical event, (NBC). Collective protection is an important aspect of fixed site defense. Ideally, it provides a contaminate free environment for people, ...

. In a civilian context the same principles of filtration and

positive pressure Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently, if there is any leak from the positively pressured system it will egress into the surrounding environment. This is in ...

is used in

positive pressure personnel suit Positive pressure personnel suits (PPPS)—or positive pressure protective suits, informally known as "space suits", "moon suits", "blue suits", etc.—are highly specialized, totally encapsulating, industrial protection garments worn only with ...

References

Chemical, biological, radiological and nuclear defense {{Nuclear-warfare-stub

See also

References