How often do terminal HEPA Filters need to be changed?

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HEPA filters (H13 and H14) are usually used as terminal filters in cleanrooms, cleaning the supplied air to the required particulate purity. Only if these filters function properly, a cleanroom can have the required purity. For this reason, these filters are subject to regular inspection and must be replaced when necessary.

Here also lies the answer to the question of how often these filters must be replaced: when necessary.

It is necessary if:

• damage is found in the filter or on the filter seal during the leakage test 
• the pressure loss at the filter exceeds a filter resistance specified for the ventilation system

But: the measurement of the filter resistance does not replace the filter integrity test!

An interval defined by the company operating a clean air system is possible from a GMP point of view, but no general interval can be defined, since the increase in pressure loss depends on:

• the aerosol concentration of the environment 
• the type and number of prefilters 
• the interval between pre-filter replacements

Companies that determine the regular replacement of filters in internal SOPs do so because of a risk consideration - avoiding to miss the time when the filter replacement would have been necessary. However, a correctly installed and correctly operated HEPA filter can be used for 10 years or more.