How Often Are HEPA Filters Replaced?

In the pharmaceutical industry, HEPA Filters play a crucial role in keeping production areas clean, especially in sterile environments. They are mandatory in sterile production, although they are sometimes also used in the manufacture of solid or semisolid dosage forms. Amongst the HEPA or high-efficiency particulate air filters are Filter Classes H13 to H14 (DIN 1822), the latter with a retention rate of 99.995%.

But the most important question is, how often do they need to be changed?

Many companies have internal policies that require replacing HEPA Filters every year, regardless of their condition. But is that really necessary? An exact number, meaning the maximum duration of use for HEPA filters in months, cannot be found in the relevant GMP guidelines. According to GMP, the filter has to be free of leaks. This is verified by qualification and regularly performed leak tests as per ISO 14644-3, which are mandatory for sterile facilities. According to the technical interpretation of the Annex 1 (PIC/S PI 032-2), leak tests are to be performed every six months in A/B zones and every twelve months in C/D zones. The FDA Aseptic Guide demands a regular inspection. The requirements of Annex 1 can be applied here as well. Leaks may be repaired; those repaired areas may only take up 0.5% of the filter surface per filter.

However, leaks aren’t the only concern. Over time, filters accumulate dust and particles, increasing airflow resistance, which means the ventilation system has to work harder to maintain proper air circulation. This pressure drop at the filter can increase to the performance limits of the ventilation system. To protect the HEPA Box, preliminary filters are used - usually fine particulate air filters like F7 und F9 filters (EN779). Those have to be replaced regularly and protect the HEPA filters from clogging.

From a practical standpoint, filter longevity is directly linked to pressure drop. Changing the filters only makes sense if the pressure drop gets too high for the performance of the ventilation system or if the cost of energy demand lies above the cost of a filter change. The filters do have to pass the leak tests (see above), of course. In practice, several companies do not use a filter for more than eight years. As mentioned before, though, this is not a legally binding value, but merely based on experience.