This is not an easy question to answer. There is no general rule or regulation as to how often filters need to be changed in a cleanroom application. Our filters typically run for several years without needing to be changed. However, the service life varies considerably depending on the application.

As a general rule, the more particle-laden the incoming air (either from the outside or from the process inside the cleanroom), the faster a filter will become clogged. For example, in a cleanroom with high particulate emissions, the filters will clog more quickly if the FFU is connected directly to the cleanroom than in a closed system where the already filtered air is recirculated. In clean room production with high particle emissions, the filter will clog more quickly than, for example, in pure inspection work.

So you can't say for sure. We have a customer who has been using original filters in his cleanroom for over 20 years without any loss of performance. But this is admittedly rather unusual.

If a filter becomes clogged with particles over time, its airflow will decrease. It is therefore important to check the condition of the filter regularly and replace it before its performance deteriorates too much. This will affect the air exchange rates and differential pressures in the room. If a filter fan unit does not have a clogging indicator, the performance is checked at the latest during regular maintenance or air velocity measurements. The individual filters are identified and replaced if necessary. As filters become clogged slowly, small adjustments to the fan speed of the FFU during maintenance can also indicate that a filter change is due in the next year and can therefore be planned.

If you also need to keep an eye on micro-organisms for the manufacture of your products, a risk assessment should consider the allowable filter life, which must also prevent contamination by micro-organisms. There is a risk that airborne micro-organisms could become trapped in the filter and multiply under unfavourable conditions. In the worst case, germs could break through the filter side. Again, there are no regulations, but it is advisable to replace filters routinely every 3-5 years or to continuously test airborne microorganisms and monitor trends.

Ultimately, it is the responsibility of the cleanroom operator to develop a maintenance programme to ensure that filters are changed in a timely manner to maintain the cleanliness of the environment.