Infections with SARS-CoV 2 indoors pose particular challenges for occupational safety and health, whether pupils and students are concerned or employees. Infection occurs when aerosols containing viruses are inhaled. The risk of getting infected can be minimized by dilution of virus-containing aerosols with fresh air. The use of air cleaners might be useful in rooms without technical ventilation and limited possibilities of air supply via open windows. Air cleaners use different principles to segregate or inactivate viruses: e.g. electrostatic precipitation, filtration, UVC-radiation, ionisation or ozonation.
The efficacy of those methods for the segregation of particles has been shown several times. This is also true for particles containing infectious viruses. When filtration is used as a principle of segregation, the inactivation of viruses is obtained after particle segregation by thermic disposal of contaminated filters. The effectiveness of other principles of inactivation used in those instruments has not yet been demonstrated.
The German Social Accident insurance, with support from IFA, therefore encourages a project to fill this knowledge gap. The aim is to develop a test method for the verification of the efficacy of air cleaners concerning the inactivation of infectious viruses in indoor air. The effectiveness of an air cleaning device is considered proven when the amount of infectious viruses in the testing atmosphere is reduced significantly (a reduction by more than 103 plaque-forming units in virus analysis by plaque-test) and sustainably. Testing results should be reproducible and independent of the background exposure. In addition to the biological effectiveness, potential hazardous effects stemming from the device or the method it uses should be considered: e.g. UV-radiation, release of chemical hazardous substances like ozone and nitrogen oxides, emission of noise. Furthermore, physical parameters like air velocity and volumetric flow rate of the device have to be considered.
Dr. Annette Kolk, IFA
Head of Section Biological agents