Scientists: Only H14 hepa air filters really help - UV light is officially advised against
Munich, Germany - 23 September 2020 - Air purifiers with H14 hepa filters are by far the safest way to protect health in autumn and winter compared to ventilation and other technologies. This is the result of research by Professor Dr. Christian Kähler of the University of the German Armed Forces in Munich. Because: Aerosols contribute significantly to the spread of the corona virus. When emitted when speaking, sneezing or coughing, they float as carrier particles in the room for hours. The University of the German Armed Forces Munich has now proven in studies that air purifiers with H14 hepa filters almost completely eliminate virus-contaminated aerosols. With regard to the cold season, these air purifiers are the best solution for companies, restaurants and schools to safely reduce the aerosol concentration in closed rooms below an infectious level. Before purchasing, it is therefore advisable to carefully check the product performance offered: For example, commercially available odour eliminators are now declared as 'virus killers' or 'disinfection devices'. Also the volume of air cleaned per hour should be taken into account. An official catalog of criteria is thus necessary to safeguard health and investments.
This makes it necessary for the Federal Ministry of Health to set out clear criteria for the procurement of air purifiers for pandemic prevention in schools, companies and the catering trade. With his new study, Prof. Dr. Christian Kähler has now also presented the necessary basis for safe school operation. The studies carried out by Prof. Dr. Kähler from the Institute of Fluid Mechanics and Aerodynamics at the University of the German Armed Forces in Munich prove that indoor air cleaners effectively reduce the risk of indirect infection by aerosols. This requires the use of automatically decontaminating H14 hepa filters and at least six air changes per hour. This ensures effective aerosol dilution and separation in the shortest possible time. Devices without these features are therefore not suitable for pandemic prevention.
Technical explanation: H14 Hepa filters offer a 10-fold higher filter performance than H13 Hepa filters, whose filter performance is still comparably good in the size range of bacteria. However, there are significant differences in the so-called MPPS range (Most Penetrating Particle Size), i.e. in the filtering out of viruses and aerosols. Here, the Laboratory Technology Project Group (ELATEC) of the Federal Institute for Occupational Safety and Health expressly advises in its statement on the topic of "Use of HEPA filters in ventilation and air-conditioning systems (Decision 16/2010)": "The HEPA filters should at least correspond to Class H14 according to DIN EN 1822-1.
In principle, the WHO, among others, advises against using UV light for "disinfection". According to the German Federal Office for Radiation Protection, the same applies to UV-C radiation equipment, the use of which without protective clothing is also harmful to health. Likewise, the Indoor Air Hygiene Commission (IRK) points out in an official communication that ionization or ozone disinfection devices are unreliable in eliminating viruses and, depending on the room, even worsen the air quality.
Technical explanation: The Indoor Air Hygiene Commission of the Federal Environment Agency in the Federal Health Gazette 2015 - 58:1992 expressly warns against the use of "air purifiers that promise to remove or chemically "convert" harmless substances (water, carbon dioxide) from gaseous organic compounds, odorous substances and bioaerosols" as long as there are no standardized test procedures for these so-called disinfection devices. The IRK also expressly opposes the use of devices that promise to clean the air by means of "atmospheric oxygen activation" or "ionization". The use of such devices, which are mostly sold as so-called disinfection devices, can lead to time-limited cleaning performance for individual substances in individual processes. However, some air purifiers release unpredictable secondary compounds into the indoor air, which cannot be conclusively assessed from a health point of view at present. The Commission therefore advises against the use of such devices as long as there are no recognized standardized test procedures for their approval and a health hazard for room users cannot be excluded in all cases.
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