Rediair uses HEPA-14 filters - these remove at least 99.995% of particles, down to 0.3µm - small enough to trap allergens, individual bacteria, fungi and viruses within aerosols.
Whilst some viruses can be smaller than 0.3µm, they do not typically exist in this 'naked' state in isolation - instead, they exist in the form of droplets and aerosols when expelled into the air, e.g through talking, coughing or breathing. These droplets and aerosols are large enough to be trapped by the HEPA-14 filters found in Rediair.