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High efficiency filter detection in biosafety cabinets

PAO aerosol concentration upstream of the high efficiency filter in the biological safety cabinet: When the photometer selector valve is turned to the left from the "CLEAR" position (both UPSTREAM positions), the display will show and record the aerosol concentration collected upstream of the high efficiency filter. When it is confirmed that the light scattering intensity of the aerosol concentration should be at least equal to the light scattering intensity produced by 10 μg/L PAO, the reading is adjusted to 100. When the aerosol concentration upstream of the HEPA filter is shown to be less than the light scattering intensity produced by 10 μg/L PAO, the reason should be checked (the compressed air supply to the aerosol may be insufficient or the pressure valve of the photometer may not be adjusted to its corresponding position)
To test the aerosol leakage rate of the downdraft HEPA filter: unscrew the screws of the top plate inside the biosafety cabinet and carefully remove the top plate behind the sloping side (taking care not to touch the lamp on the inner wall). Set the selector valve to the "DOWNSTREAM" position and move the photometer probe 25 mm downstream of the filter from the filter surface at a scanning rate of less than 50 mm/s so that the probe sweeps the entire downstream side of the filter and the edges of each combination filter, with a slight overlap of the scanning path.
Aerosol leakage rate test around the perimeter of the downdraft HEPA filter: The photometer probe is moved around the entire perimeter of the filter, along the joint between the combination filter and the frame, 25 mm from its surface, at a scanning rate of less than 50 mm/s. The maximum value is carefully checked, read and recorded.
Exhaust HEPA filter aerosol leakage rate test: The photometric probe is moved 25 mm around the entire surface of the exhaust HEPA filter at a scanning rate of less than 50 mm/s and is carefully inspected, the maximum value is read and recorded.
Aerosol leakage rate test around the perimeter of the exhaust HEPA filter: the photometer probe is moved around the entire perimeter of the exhaust HEPA filter, along the joint between the combined filter and the frame, 25 mm from its surface, at a scanning rate of less than 50 mm/s, examined carefully and the maximum value is read and recorded.
YY 0569-2011 5.4.2.1 specifies that the leakage rate of the filter should not exceed 0.01% at any point, with the maximum value being read and recorded in the inspection log. When the leakage rate exceeds 0.01%, the scan shall be repeated several times and the maximum displayed value and the orientation of the excess leakage rate shall be recorded and a sketch drawn.
Evaluate the results according to YY 0569-2011 5.4.2.1 "The leakage rate of the filter shall not exceed 0.01% at any point" and give a conclusion as to whether or not it passes.

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