scope:

This Recommended Practice (RP) covers definitions, equipment, and procedures for leak-testing highefficiency particulate air (HEPA) filters and ultralowpenetration air (ULPA) filters in the factory as they are produced, at the job site before they are installed, and after they are installed in cleanrooms and in unidirectional- flow, clean-air devices. When used in conjunction with other RPs, including IEST-RP-CC001, IEST-RP-CC002, IEST-RP-CC006, IEST-RP-CC007, IEST-RP-CC021, and IEST-RP-CC028, this RP may be used to define the basis of an agreement between customer and supplier in the specification and procurement of HEPA and ULPA filters, and in the testing of unidirectional-flow, clean-air devices and cleanrooms.

This RP also includes procedures for measuring the uniformity of the aerosol challenge approaching the filter under test.

BACKGROUND AND PURPOSE

HEPA and ULPA filters such as those used in cleanrooms and clean benches are tested for particle removal efficiency and resistance to airflow when they are manufactured. Frequently, these filters are scanned for leaks as an additional precaution. This scanning is performed by the filter manufacturer before the filters are packaged and shipped. The scan test may be repeated as a field bench test when the filters are unpacked at the customer's location before the filters are installed. If product is exposed or located immediately downstream of the HEPA or ULPA filter(s), a scan test is often performed after the filters are installed to verify the integrity of the filter and its installation. Typically, the scanning is repeated at regular time intervals to verify the continued integrity of the filtration system. If the filters are remote to the cleanroom (clean zone), a test to determine the total leakage of the filter installation is adequate.

Leak-testing HEPA and ULPA filters is one important part of verifying their performance. Other tests, such as those described in IEST-RP-CC001, IEST-RP-CC002, IEST-RP-CC006, IEST-RP-CC007, and IEST-RPCC028, are also important for characterizing the performance of HEPA and ULPA filters, clean-air devices, and cleanrooms.

The choice of which test procedures are required depends on the performance level of the filters, clean-air device, or cleanroom, and on the intended application. Specific test requirements are the result of an agreement between customer and supplier.

This RP provides a set of recommended procedures for testing HEPA and ULPA filters for leaks. Two methods are provided for scanning the downstream surface of HEPA and ULPA filters for leaks. One method is provided for determining if there are leaks in inaccessible HEPA and ULPA filters. Section 5 provides guidance for selecting the appropriate leak-test method.

When purchasing HEPA or ULPA filters, or a cleanair device or cleanroom containing HEPA or ULPA filters, the appropriate sections of this RP should become part of the purchase order to define the expected performance of the filters as received.