HEPA Filter is originally called a high-efficiency particulate absorber. It is a type of air filter, also known as a high-efficiency particulate trap. Air filters, which are in the HEPA filter standard, have application areas covering many sectors such as clean rooms, medical facilities, automotive and aviation.
To qualify a filter as a HEPA filter based on industrial standards, that filter must capture 99.97% of particles larger than or equal to 0.3 µm in size (particles in the air passing over the filter).
HEPA Air filters should be tested to a recognised and current performance standard – many products use the term ‘HEPA’ without an appropriately certified test. HEPA filters that are marketed where MPPS is simply ‘believed to be 0.3μm’ is not appropriate for today’s HEPA applications. All UK /European HEPA filters should be individually tested and certified to EN 1822:2019
HEPA filters are a kind of felt composition of randomly arranged fibres. These fibres are usually composed of glass fibres. They have a diameter between 0.5 µm and 2 µm. The main factors affecting the capture functions are the fibre diameter, the thickness of the filter and the face velocity. The air gap between HEPA filter fibres is usually more than 0.3 µm. The fact that this gap is more than 0.3 µm gives rise to the common and incorrect assumption that smaller particles can easily pass through the largest gap between the fibres of a HEPA filter, and in this case, the filter will act as a sieve.
Unlike porous membrane type filters, where particles as large as the largest gap or opening distance between the fibres cannot pass, HEPA filters are designed to capture smaller sized pollutants and particles.