What standards must a HEPA filter meet?
HEPA represents the ability to meet a series of strict requirements. In Europe, HEPA filters must remove 99.95% (ISO) of particles, while in the United States, they must remove 99.97% of particles with a size of 0.3 um or larger. Filters that exceed the requirements of HEPA and capture more than 99.999% of particles are called ULPA filters or ultra-low penetration air filters. These filters are expensive because their efficiency and medium resistance levels are higher. To protect HEPA filters, pre-filters are used: usually fine particle air filters, such as F7 and F9 filters (EN779). These must be replaced regularly to prevent HEPA from clogging and affecting air volume.
Why is the frequency of HEPA filter replacement a key issue?
The integrity of HEPA filters is crucial for ensuring the cleanliness level required in a cleanroom. However, when deciding how often to replace the filters, there are other related aspects that are also worth considering. One of these is the load and pressure drop of the filters. If the pressure drop is too high, the ventilation system will start to work at a higher speed to maintain the required air exchange rate, resulting in higher energy consumption. In this case, if our operating costs increase significantly, the HEPA filter is more likely to be worth replacing.
Regulatory Requirements of GMP, ISO and ISPE Guidelines
There are no specific regulations for the maximum service life of HEPA filters in GMP, ISO and ISPE guidelines. However, the leakage inspection requirements for HEPA filters are clearly defined. Both GMP and ISO 14644-3 guidelines stipulate that leakage tests must be conducted at least once every 6-12 months. It is worth noting that according to GMP, the filter must be leak-free. In ISO 1-5 level areas, leakage tests must be conducted every six months, and in ISO 6-9 level areas, they must be conducted every twelve months. Of course, if this HEPA filter fails the test, it must be replaced or repaired.
Best Practice for HEPA Filter Replacement Frequency:
By installing online differential pressure gauges to monitor the load (i.e., pressure drop) of front-end filters such as primary and intermediate filters, and replacing or cleaning them regularly, it is evident that adequate upstream primary and intermediate filters can extend the service life of HEPA;
Periodic maintenance checks for any damage or mold on HEPA filters, and replace them based on the inspection results;
Periodic monitoring of HEPA load and pressure drop. If it reaches twice the initial pressure drop, replace it based on the load definition;
Refer to regulatory requirements to test the leakage rate. If the leakage rate is greater than 0.01%, replace it based on the leakage rate definition;
Test relevant indicators related to the environmental level, based on environmental parameters such as particle count and microbial results, define and replace;
For critical areas such as A-class areas, replace the HEPA filter when adverse airflow models are detected during monitoring.
Suzhou Pharma Machinery Co.,Ltd.
2026/01/09
Tia
