ETL 1110-3-498
24 Feb 99
APPENDIX B
COLLECTIVE PROTECTION FOR FACILITIES
B-1. Collective Protection Design Strategy.
A chemical, biological, or radiological (CBR) airborne threat can come from a wartime attack,
terrorist attack, or from an industrial accident. Protection of personnel during these events can be
achieved by evacuation from the affected area, collective protection sheltering, or individual
protective equipment (IPE).
a. Use of CBR Detectors. Theoretically, automatic detectors can be used to initiate
protective actions such as shutdown of ventilation systems, closing outside air intakes, or turning
on filtration systems. Detection of radiological agents can be performed with off-the-shelf
equipment. Current biological detection technology requires a minimum delay of approximately 15
minutes to detect the presence of biological agents. Practical application of chemical detection is
limited by shortcomings in response time, false alarms, broad spectrum capability, maintenance
requirements, cost, and the quantity of sensors needed at air intake locations. For wartime threats,
audible and visual indicators along with detection are used to initiate protective actions. For
terrorist threats, no audible and visual indications announce the attack, other than incapacitation of
people. Thus, application of detectors for terrorist threats should be limited to the following uses:
first entry determination by first responders, monitoring casualties before medical treatment,
determining the extent of the hazard, and determining when protective measures are no longer
required.
b. Wartime Threat. For large scale wartime chemical or biological attack, the facility will be
designed to provide a toxic-free area (TFA) where personnel can function without IPE. To resist
the penetration of agents into the TFA from long duration exposure, a wartime facility must have a
CBR overpressure filter system that prevents penetration of agents at a wind speed of 40 km/hr
(25 mph). Also required are an outdoor or integral contamination control area (CCA) for
decontamination of personnel and an airlock that prevents contaminated air from entering the TFA
during ingress and egress of personnel.
c. Terrorist Threat. For facilities that require continuous operation during a short duration
threat with little or no warning, such as a terrorist attack, continuous filtration of the ventilation air
intakes is required. To resist the short duration penetration of agents into the TFA, a CBR
filtration system will be required to provide an overpressure that prevents the penetration of agents
through the TFA envelope at wind speeds of 12 km/hr (7 mph). This wind speed condition is most
favorable for directing a plume of agent with minimum dispersion toward an outside air intake.
d. Industrial Accidents. To provide passive protection for an exposure of short duration,
sealing measures at the facility envelope and closing outside air intakes will provide limited
protection to the occupants for a short period of time. The level of protection provided by passive
B-1
Previous Page
