ISO14644 recommends a maximum time interval of 24 months for leak detection of installed HEPA. DOP leak detection should be performed after HEPA installation or replacement. When environmental monitoring indicates deterioration of air quality, or when the product sterility test fails and the culture simulation filling test fails, the leak detection can be performed as part of the deviation investigation. Filters that require a leak test also include HEPA used in drying tunnels and dry ovens.
