To determine if the HEPA filter itself and its installation have significant leakage, the following must be tested on site: filter media, filter media in its frame, between the gasket of the filter frame and the filter set support frame, between the support frame and the wall or ceiling.
Materials and instruments for DOP leak detection include: dust source (PAO solvent), aerosol generator, and aerosol photometer. The aerosol generator is an ATITDA-6C. Handheld Laskin nozzle type aerosol generator that uses air directly without the need for compressed gas as a power source. At a working pressure of 20 Pa, a gas flow rate of 50 to 2025 f3/min produces a polydisperse submicron oil aerosol of 10 to 100 ug/mL. The aerosol photometer used was an ATI2H photometer with a dynamic measurement range of 0.00005 to 120 ug/L and a sampling flow rate of 1 F3/min (28.3 L/min).
A PAO aerosol is introduced on the upstream side of the HEPA to be tested. In order to achieve a uniform concentration of aerosol when it reaches HEPA, the aerosol can be introduced directly from the negative pressure side of the system fan. To be introduced from the duct, it should be introduced at least 10 times the diameter of the duct from HEPA and minimize the bend. Under normal circumstances, the upstream aerosol is kept at the required concentration, and the concentration fluctuation can be within a certain range. For the laminar flow hood, HEPA on the clean bench, the aerosol is introduced directly from the negative pressure side of the system fan.
The aerosol photometer is initialized, and the 100% and 0% reference standard values are initialized according to the aerosol photometer operation requirements, and the alarm value is set. Connect the UPSTREAM sampling tube to the upstream sampling port to measure the concentration of the upstream aerosol. Adjust the aerosol concentration to occur according to the aerosol generator operation requirements, so that the upstream aerosol concentration reaches 10~20ug/mL.