High Efficiency Particulate Arrestance filters, sometimes referred to as High Efficiency Particulate Air filters, or HEPA filters for short, are an integral part of air purification and cleaning systems, with a range of applications. These thin microfiber filters are used in clean-rooms, bio-safety cabinets and other laboratory technology, as well as air conditioners and vacuum cleaners. In this article, we will focus on HEPA filters used in industrial settings – specifically looking at the when, why and how to replace them.
HEPA filters are highly efficient, filtering out 99.99% MPPS. MPPS stands for Most Penetrable Particle Size, being 0.3µm in diameter. In so doing, they can provide protection against harmful organisms and contaminants. However, HEPA filters do not last forever. As time goes by, particulate builds up in the intercepting filter, and eventually the maximum load is reached.
The length of time that a HEPA filter will last depends on a number of factors. One factor is the environment in which it is used – for example, the laboratory and the processes performed there, and subsequent particulate load. Another is the frequency with which the filter is used (many are used continuously). A filter could last several years, or only a few months.
It is important to conduct regular checks on the airflow through the filter. When this becomes impeded, it indicates that the filter needs to be replaced. Of course, if the filter is leaking at all or shows any other signs of damage, it needs to be changed or repaired immediately. Routine DOP tests prove filter integrity and indicate defects. And filter pressure drop monitoring provides guidelines to ensure your filters are changed before they reach their maximum load capacity.
HEPA filters generally have pre-filters to lessen the workload and enhance their efficiency. These need to be changed more frequently – generally every few months. If this is done correctly and consistently, the life of the HEPA filter itself can be significantly extended.
Removing a HEPA filter and installing a new one is a process that needs to be handled carefully to ensure the safety of workplace personnel and prevent damage to the filter. If mismanaged, it could result in exposure to high concentrations of harmful organisms. If the HEPA filter is part of a bio-safety cabinet, a full decontamination must be done using gases to neutralise the threats. It is also possible to use a bag-in, bag-out system in some cases. This is where the old filter is removed in a sealed bag, and a new one inserted in a sealed bag. However, this needs to be set up when the filter-containing equipment is initially installed and all servicing must be carried out by trained personnel.
The risks involved in replacing HEPA filters, particularly in laboratories, necessitate the involvement of suitably qualified, experienced technicians. It is best to ask a reliable, reputable company to perform the whole process. This ensures protection of the workplace, staff and surrounding environment - providing peace of mind. Where the filter is part of a bio-safety cabinet, the technicians would also be able to certify the equipment after replacing the filter.
