24 Feb 99
E-1. Collective Protection System Design.
If the CP filtration system is located in a contaminated environment; i.e., outside the TFA
envelope, the CP filtration system will be designed as a blow-through system with the blower
located before the CP filtration system. If the CP filtration system is located in a clean
environment; i.e., inside the TFA envelope, and draws in the contaminated air through a ductwork
system, it will be designed as a draw-through system with the blower located after the CP filtration
system. The CP filtration system blower total static pressure will be designed to include the
filtration system with dirty filters, ductwork system pressure losses, and the overpressure
requirement of the TFA.
E-2. Filtration Systems.
The filtration system is the most critical part of the CP overpressure system. A number of filtration
systems are available from both the military and commercial suppliers. If commercial filter systems
are used, the mechanical system designer should have the technical expertise to prepare
specifications that meet military filter system requirements. For continuously operated filter
systems, accessory equipment such as moisture eliminators and large particulate filters will be
considered for protection of the filter system.
a. Military Filtration Systems. Military filtration units are typically provided as
Government-furnished equipment (GFE). Military equipment provided as GFE has the advantage
of being pre-approved for use on Government installations, while commercially available
equipment requires additional Government quality testing.
(1) Fan Filter Assembly (FFA) 580. The FFA-580 filtration unit provides chemical
filtration with a designed capacity of 283 L/s (600 cfm) at 3,750 Pa (15.0 inches wg) using a 2.24-
kW (3-HP) motor. The FFA-580 contains a HEPA filter and an ASZM-TEDA carbon adsorber
designed for a residence time of 0.25 seconds. The FFA-580 is designed for standby operation and
is not intended for continuous duty.
(a) Air Tempering. The FFA-580 unit does not provide air tempering of the filtered air.
For Class I and II facilities, the filtered air can be either ducted directly into the facility air handling
unit return ductwork or discharged directly into the TFA. The existing mechanical system
provides tempering of the air and must be located within the TFA envelope. If the FFA-580 unit is
used to pressurize Class III facilities, the filtered outside air will be discharged directly into the
TFA and the TFA temperature will approach outside ambient conditions.