While the World Health Organisation (WHO) is continuing to assess ongoing research on the transmission of coronavirus (COVID-19), we are recommending the use of HEPA filters in air handling units to ensure the best level of protection for all. HEPA filters are used as a final stage of air filtration in air handling units in buildings that require a higher level of contamination control, such as hospitals, research laboratories, pharmaceutical manufacturing plants and certain food production facilities. HEPA (high efficiency particulate air) filters offer further protection from microbial contamination.
HEPA filters are made up of countless randomly-arranged matted fibres. They are designed in this way to trap very small particulate contaminants from an air stream by:
Interception – A contaminant particle passes within a distance equal to one particle’s radius of a fibre. This results in the particle touching the fibre and being removed from the airflow. Particles further than one particle’s radius from a fibre will not be trapped.
Inertial Impaction – Due to inertia, large particles (usually 5–10 µm in size), are unable to adjust to the change in direction of air near a filter fibre and become trapped on the fibre.
Diffusion – Small particles (usually 0.1 µm or less in size) travel in an erratic fashion as they interact with gas molecules (Brownian motion). Their random and erratic motions cause them to become stuck in filter fibres.
Be aware that HEPA filters are tested in a different way to other filters, so when purchasing this type of filter, you must ensure it has been tested to BS EN 1822:2009. A test certificate must be supplied with each filter detailing the tested efficiency. The BRCGS Food Safety Issue 8 recommends that HEPA filters are “integrity-tested after installation and then on a periodic basis as per ISO 14644”.
HVDS are currently increasing their supply of H13 HEPA filters (99.5% MPPS EN1822) due to requirements by the health and medical organisations (including the NHS) and the food manufacturing industry. Although these filters are classed as Hospital HEPA Grade, they can be installed into most AHU systems, replacing existing filters.
See our range of HEPA filters here.
If you are unsure whether your level of filtration meets the required standard in your building and would like a full risk assessment by our air filtration and ventilation specialists, contact us on 01785 256976 or get in touch here.