In the second stage, a bed of activated carbon impregnated with copper, silver, zinc, molybdenum, and triethylenediamine (commonly referred to as
ASZM-TEDA) adsorbs chemical aerosols and gases.
Made by Hunter Manufacturing Company of Solon, Ohio, the unit uses a high-efficiency particulate arrestance (HEPA) filter to remove 99.97 percent of biological agents, chemical aerosols, and radioactive particles at 0.3 microns, in addition to an integral
ASZM-TEDA activated carbon filter to remove 99.999 percent of NBC agents in gaseous or vapor form.
An M56A1 filter set, which consists of a Hepa-grade particulate filter fitted inside an activated carbon gas filter, utilises
ASZM-Teda activated carbon to remove gaseous chemical agents.