Fresh air filters remove toxic particles and chemical agents in aerosol form and biological materials at an extremely high efficiency rate. The filters are standard filters used in filtration units to supply purified air to individual vehicle members when positive cabin pressure cannot be maintained. These types of systems are also used as NBC backup systems in many (sealed) armoured vehicles that normally use overpressure in the crew compartment.
Prefilters are also available that remove sand, dust, and fine dust from the air intake, before it comes in contact with the NBC filter. All Beth-El filters are tested and certified with international authorities and, as well, have been field tested under actual circumstances.