Guard bed for gas particulate filter in collective protection system

Shields collective protection filters from degradation by common contaminants as well as other toxic chemicals

Materials Environmental
An airman removes a filter from the housing of a breathable air filtration system during a test of the Survivable Collective Protection System. (Air Force photo)

Collective protection (CP) air filters, the most common being the military’s M48A1 and the M98 filters, are designed to remove toxic compounds from the air in ground vehicles, field hospitals, command posts, and ships, as part of an overpressure system, creating a toxic-free¬†area for personnel during nuclear, biological, or chemical weapon attacks.

In their simplest form, a CP filter allows air to flow through a gas filter bed of activated, impregnated carbon media in a manner that facilitates contact between the airstream and the carbon media. CP filters may be in operation on a continuous or near continuous basis, processing large volumes of air during their lifetime.

While effective at removing toxins, CP filters can be degraded by common ambient air contaminants including sulfur dioxide, nitrogen dioxide and vapors from diesel, jet, and auto fuel. To address this situation, a team of Army and Navy researchers developed an initial filter, called a guard bed, situated upstream of the CP, which can remove filter degrading compounds.

The filter material contains zirconium hydroxide loaded with base metals (copper, zinc, cobalt), triethylenediamine, and microporous activated carbon. This inexpensive, replaceable filter is expected to greatly lengthen the effective life of the CP filter and provide additional protection to people operating in at-risk environments.

The M98 filters are used on:

  • U.S. Military M84, M95, and M96 filtration systems
  • U.S. Air Force Multiple Cell Radial Filter Housings
  • U.S. Army buildings and transportable shelters

They could also be used to filter air in hospitals, subway tunnels, bunkers or safe rooms.

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