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Type C1 Exhaust HEPA Filter Leak Test
During this test the exhaust HEPA filter will be challenged and a downstream average
utilized to check for leaks. This section describes how to test the exhaust HEPA filter
on a Type C1 biosafety cabinet. The aerosol generator and photometer should be
prepared at this point as described in the preparation steps listed in the previous
section.
1. If the biosafety cabinet is connected to an exhaust system, secure the Inlet Relief
Valve in an open position (to keep the cabinet’s blowers running during the test).
Then remove the perimeter screws that secure the front plate of the exhaust
housing. Set the front plate aside. See Figure 10-23 for reference.
2. Set the photometer sampling valve to “DOWNSTREAM”. Ensure proper vacuum
at the sampling tube.
3. Open the appropriate number of Laskin nozzles on the aerosol generator (see
Table 10-5).
4. Using a rigid tube (18 inch long x 3/8 inch OD) connected to the photometer
probe pickup (see Figure 10-24), scan the downstream side of the filter, resting
the tube in the ridges located on the top of the opening (see Figures 10-24 &10-
25). By resting the tubing in successive ridges, and alternatively pushing the
probe in on the first ridge, then shifting the tube to the next ridge, and pulling it
out, you can quickly scan the filter surface in overlapping strokes. By resting your
index finger under the tube during scanning, you can accurately control the probe
position and height.
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