Since World War I, carbon filtration had been used exclusively for both individual and collective protection systems against the threat of chemical warfare agents. The addition of a high efficiency particulate air (HEPA) filter in conjunction with a carbon filter provided the necessary protection against biological agents.

Until recently this method of filtration was adequate to address the chemical and biological threat. However, in recent years chemical warfare agents have been developed and labeled as "carbon breakers" or "filter penetrates" for which currently available carbon filters provide only limited, if any, protection.

Pressure swing adsorption (PSA) technology, a regenerable process, offers a solution to this challenge through its ability to remove chemical warfare vapors, including the "carbon breaker" class of compounds. A properly designed PSA will remove to below detectable levels all known chemical warfare vapors.

Pall Corporation has been intimately involved in PSA since its development in 1956. This experience has aided Pall greatly in achieving its present preeminence in the design and manufacture of PSA for nuclear, biological and chemical (NBC) protection.

Pall's regenerable filtration system for NBC comprises two filtration components. The first is a water separator, coalescer HEPA (WSCH) filter that removes entrained liquids by centrifugal separation, liquid aerosols by coalescing, and traps particulates with an efficiency greater than 99.97% for 0.3 microns. The WSCH removes radioactive particles, biological contaminants, and chemical agents, whether delivered as liquids or as aerosols. The second component is a PSA that removes all chemical warfare agent vapors. The combination of these two filtration components makes up the Pall NBC regenerable filtration system.

PSA lends itself to the full spectrum of chemical warfare collective protection applications. However, a PSA system is at its best when completely integrated with an environmental control system, so the product air delivered to the crew of an armored vehicle, aircraft, command and control shelter or marine vessel is not only free from chemical contaminants, but is also temperature controlled for the comfort of the crew. A PSA system requires a source of pressurized air to operate, as does an air cycle machine-based environmental control system. This pressurized air can come from either "bleed air" provided by an engine or other power source, or from a compressor when bleed air is not available.