DO HEPA FILTERS KEEP VIRUSES?

DO HEPA FILTERS KEEP VIRUSES?

HEPA (High Efficiency Particulate Air) filters are a special type of air filter that has the capacity to retain particles with high efficiency. They are generally used in clean room systems, hospital operating rooms, pharmaceutical production facilities, laboratories and similar sensitive environments.

HEPA filters are made of a very dense filter material that traps various particles, including large amounts of microorganisms, as it passes air flow. A standard HEPA filter has a high particle capture efficiency and traps approximately 99.97% of particles 0.3 microns in size.

Particles and microorganisms have different mobility. Microorganisms attach to particles and move in the direction of air flow. It has been determined that while the particles adhere to the nanoporous filter structure, more flexible and smaller sized microorganisms can easily pass through the filter pores. Therefore, it has become inevitable to perform particle and microorganism tests separately.

HEPA filters are classified according to their efficiency in capturing particles of certain sizes according to ISO 16890 and EN 1822 standards. However, since they have not been subjected to microorganism capture tests, unfortunately it has not been proven which microorganisms they can capture and with what efficiency.

Standards and methods for airborne microorganism measurement are generally used to monitor and control air quality in clean rooms, hospital environments, the food industry and laboratories. Here are some standards and methods commonly used in this field.

ISO 14698-1 and ISO 14698-2 Biocontamination control: Specifies general principles and methods for identifying and controlling microbial contamination. In particular, it provides guidance for air sampling, bioparticle counting and microbial analysis.

TS 13848 Microbial Gel Air Filter: The standard developed by TSE and for which I serve as the subject rapporteur, briefly explains the necessary principles and methods by determining the limits for the determination and control of airborne microorganisms.

MICROORGANISM RETRACTION EFFICIENCY OF HEPA FILTERS

There is no accepted international standard regarding the capture of microorganisms from the filter surface and the determination of its percentage rate. However, there are various studies that have been done so far.

Study 1: In the system we have developed together with Ekoteks laboratories since 2019, the EN 14683 standard has been developed and larger filter media can be tested with various bacteria. As a result, the bacteria retention efficiency of filter media at high air flow rates was tested and great success was achieved. These tests were repeated with various bacteria and the same success was maintained.

Study 2: The capture efficiency was tested by passing the virus through the filter surface in a small cabin that we developed together with Yeditepe University in 2021, and great success was achieved.

Conclusion: As a result of the studies carried out in the light of this information, it has been proven that microorganism capture rates of filters can be determined by performing microorganism migration tests on the filter surface. It is inevitable for public health that these procedures are standardized and made available to the international public.

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