ETL 1110-3-498
24 Feb 99
APPENDIX F
AIRLOCKS AND PERSONNEL PROCESSING
F-1. Airlock Description.
Airlocks will be used in Class I facilities where an overpressure must be maintained during
collective protection operations.
a. Stand-Alone Two-Stage Airlock. As shown in Figure F-1, the stand-alone two-stage
airlock has outer first stage and inner second stage compartments. Clean airflow is provided by a
dedicated filter blower unit connected to the inner compartment at the filtered air inlet. The stand-
alone airlock is designed for a 94 L/s (200 cfm) filter blower unit and intended for retrofitting to
existing facilities. The outer compartment is used to remove protective garments while it is being
continuously purged by the flow of filtered air. After protective garments are removed, personnel
enter the inner compartment which is then purged of vapors during the dwell cycle. After the
dwell period, personnel enter the toxic-free area (TFA).
b. Integral Single-Stage Airlock. As shown in Figure F-2, the integral single-stage airlock
is provided with filtered air from the TFA. The overpressure in the TFA will cascade through the
airlock, thereby continuously purging contaminants from the airlock. The design airflow rate will
be determined by equation C-1. The airlock is used to remove protective garments while it is
being continuously purged by the flow of filtered air. After the protective garments are removed,
the airlock will be purged of vapors during the dwell cycle. After the dwell period, personnel
enter the TFA.
F-2. Airlock Features.
The following features are common to an integral or stand-alone airlock.
a. Timers. A mechanical bell timer to time the dwell and purge cycles is required in each
compartment.
b. Windows. A window is required at each compartment to determine if it is occupied.
c. Lights. Lights are required because the interior lacks adequate natural lighting.
d. Purge Vents. The two-stage airlock has fixed rather than adjustable purge vents because
it has a dedicated filter blower unit that makes the airflow rate easy to maintain. For an airlock
without a dedicated filter blower unit, a variable area purge vent or flow control valve is required
to adjust the airflow rate and maintain the required purge rate.
F-1
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