ETL 1110-3-498
24 Feb 99
APPENDIX C
CLASS I, FILTRATION WITH PRESSURIZATION
C-1. Existing Facility Classification.
Existing facilities can be separated into four classes that reflect their potential to support the
integration of a CP system.
a. Class IA. This class of facility is capable of fully integrating the CP overpressure system
with the facility heating, ventilating, and air-conditioning (HVAC) system. The HVAC system
may not be specifically designed for a CP overpressure system, but it is capable of fully maintaining
the facility temperature during CP system operation. The CCA will be outside of the facility or
under an open-air overhang, roofed shelter, or tent.
b. Class IB. The facility HVAC system is capable of partial integration of the CP
overpressure system. The HVAC system may require upgrades to existing ductwork and isolation
of the ductwork used for normal HVAC facility operations. The HVAC system may not be
capable of maintaining original design conditions without modification and may require
supplemental heating and cooling. The CCA will be outside of the facility or under an open-air
overhang, roofed shelter, or tent.
c. Class IC. The facility HVAC system is not capable of integrating the CP overpressure
system. The facility design temperatures cannot be maintained without supplemental heating and
cooling from the CP overpressure system. The CCA will be outside of the facility or under an
open-air overhang, roofed shelter, or tent.
d. Class ID. The facility cannot be sealed economically to maintain an overpressure, but it is
suitable for portable enclosures or liner systems set up internally with advance warning. This type
of arrangement allows the existing HVAC system to partially or fully maintain the facility design
temperature outside the inflatable liner or shelter. Examples are warehouses, hangers, and
maintenance bays.
C-2. Guidance.
New Class I CP facilities will be designed as Class 1A; i.e., capable of maintaining the facility
temperature during collective protection operations. New collective protection facilities with an
integral CCA will be designed in accordance with TM 5-855-1 and other criteria as designated by
the using command having jurisdiction.
C-1
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