Virus filtration

Viruses in their dry form are in the size of 0.08-0.12µm, but viruses are usually attached to an aerosol and hence are almost always larger in size. A ULPA filter with a separation efficiency of 99.9995%, is suitable for filtering these particles. The filter is rated ULPA 15 and tested in accordance with EN 1822-1 and has a separation efficiency of >99.9995%.

Viruses are usually between 0.08-0.125µm in size in their dry form (COVID-19 is known to be 0.125µm in size). Viruses attach themselves to biological and non-biological aerosols generated from coughing and sneezing and the use of hand-pieces, which create particle sizes in the range of 0.5-3µm. Movex LFK U has a ULPA filter (FPU 50) as standard. The filter is rated ULPA 15 and tested in accordance with EN 1822-1 and has a separation efficiency >99.9995%. The filter is tested using the MPPS (Most Penetrating Particle Size) method with a size of 0.17 µm, which is the most difficult size for a filter to capture. For smaller or larger particles, the filter has higher separation efficiency. When viruses are captured by the ULPA 15 filter, they become strongly embedded within the fibres of the filter media and will dry out and die due to the volume of air passing over the filter within a couple of days. The filter test is carried out at a flow of 100 m³/h (28 l/s) per m² filter area. At higher flows per m², the filter efficiency is reduced. Movex FPU 50 has a filter area of 5 m² and can thus tolerate a flow of up to 500 m³/h without diminished separation efficiency. The FPU 50 filter should be replaced once every 6 months.

The filter

The filter has been tested against the MPPS (most penetrating particles) method with a size of 0.17 µm, which is the most difficult size for a filter to capture. For smaller or larger particles, the filter has a higher separation efficiency. The smallest particles do not follow the Airstream but behave like gases than particulate, called “Brownian movement”. These particles are battered across the direction of flow in random “helter-skelter”. When a particle strikes a fibre, it’s retained by the adhesive forces (van der Waal forces) between the particle and the fibre.