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Preparatory work

Make sure that the HEPA Filter Box is firmly installed and well sealed.

Prepare an aerosol generator (such as a PAO generator) and a photometer.

Introduce aerosol

Introduce PAO or DOP aerosol on the upstream side of the HEPA Filter Box. If introduced from the air duct, it should be introduced at a distance of at least 10 times the diameter of the air duct from the HEPA, and bends should be minimized as much as possible.

Photometer initialization and calibration

Initialize in accordance with the operation requirements of the photometer and set the alarm value.

Connect the sampling tube to the upstream sampling port, measure the concentration of the aerosol upstream, and adjust the aerosol generator to make the concentration upstream reach 20-80 μg/L.

Scan for leak detection

Remove the diffuser plate of the HEPA and use a photometer to scan the entire filter surface, the seals between the filter and the frame, between the frames, and between the frame and the static pressure box.

When scanning, the sampling head should be approximately 2.54cm away from the filter surface. The scanning speed should not exceed 5cm/s. The scanning should be carried out in a straight line back and forth, and the lines should overlap.

Result determination and processing

The leakage rate of high-efficiency filters should be less than or equal to 0.01%.

If the leakage rate of all points does not exceed 0.01%, the HEPA Filter Box is determined to be qualified. If any part exceeds 0.01%, it is judged as unqualified and needs to be repaired or replaced.

The leakage points can be repaired with special glue, but the area of a single leakage point should not exceed 1% of the total area, and the area of all leakage points should not exceed 5% of the total area; otherwise, replacement is necessary.