ETL 1110-3-490
13 May 98
b. Existing Facilities. Existing facilities designated to have a CP overpressure system will be
modified in accordance with this appendix. Expedient collective protection sealing measures for
existing facilities without a CP overpressure system will be based on the recommendations in
ERDEC-TR-336.
c. New Facilities. New facilities designated to have a CP overpressure system, or to incorpo-
rate design features that ease future installation of a CP system, will incorporate the requirements
discussed in this appendix.
B-3. Design Requirements. Major considerations for the design of CP systems for both existing
and new facilities are listed below. Requirements for each item are discussed in subsequent
paragraphs.
a. Button-Up Period and TFA Floor Area Requirements.
b. TFA Envelope.
c. Airlock Requirements.
d. TFA Overpressure.
e. TFA Envelope Air Leakage Rate and Sealing Measures.
f. CP Overpressure System Design.
g. CP Control System and Operational Requirements.
h. Operation and Maintenance.
B-4. Button-Up Period and TFA Floor Area Requirements.
The CP button-up period is determined by the command or authority having jurisdiction and can
range from a few hours to several days. For terrorist attacks, the button-up period is usually less
than 24 hours. Button-up periods longer than 24 hours are generally restricted to wartime. The
button-up period influences the floor area requirements and the amount of consumable and waste
storage. Generally, the button-up period will not significantly affect the performance of the CP
system.
a. Less Than 24 Hours. A button-up period less than 24 hours does not require rest and relief
areas. The minimum floor area is approximately 20 ft2/person.
B-2
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