Do AC And Pipe Cleaning Have Effect On Covid-19 Spread?

- Jun 05, 2020-

ReHVA, the European Federation of HVAC Associations, recommends that humidification, air conditioning and pipe cleaning have no real effect on the spread of coronavirus.


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This information is contained in a new consultation document published by REHVA and is said to be based on the latest knowledge in the WHO document "Preparing workplaces for COVID-19".


The six-page document, which is used by air-conditioning professionals and facility managers, is limited to commercial and public buildings such as offices, schools, shopping areas, sports venues, etc., and is expected to be only occasionally infected. Hospitals and medical facilities are excluded.


Crucially, the document insists that humidification and air conditioning have no real effect on the spread of the virus. Unlike some other viruses, SARS-CoV-2 is a virus that causes Covid-19 disease, is highly resistant to environmental changes, and is only sensitive to high relative humidity of more than 80% and temperatures above 30 degrees C.


The document says the heating and cooling systems are operating properly because there is no direct impact on the spread of the Covid-19.


In addition, the document insists that pipe cleaning is not effective against infection between rooms.


Heat recovery

It is believed that the heat recovery device can transfer the virus attached to the particles from the exhaust side to the air-feed side through a leak. In rotary heat exchangers (including wheels), particles are deposited on the return side of the heat exchanger surface and may refloat when the heat exchanger turns to the air feeder side.


Therefore, REHVA recommends turning off the rotary heat exchanger during the SARS-CoV-2 event. If a leak is suspected in the heat recovery section, you can choose to adjust the pressure or bypass to avoid air leakage to the gas supply side due to higher pressure on the pumping side.


When the HVAC system is equipped with a dual coil unit or another heat recovery device that ensures 100% separation of air on the return and air supply sides, the spread of virus particles through the heat recovery device is not considered a problem.


Recirculation

When the centralized air treatment unit is equipped with a recirculating zone, the virus particles in the return pipe can also re-enter the building. Therefore, it is recommended to avoid central recycling during the outbreak of SARSCoV-2 by closing the recirculating flap.


It is also recommended that the dispersion system be switched off where possible, such as the use of a locally recycled fan coiling device to avoid re-suspension of virus particles at room temperature. The fan coil unit has a thick filter that does not actually filter out particles with viruses. If it is not possible to close, these units should be included in the cleaning activity as they may collect particles like any other surface in the room.


The document is also contrary to recent assertions that pipe cleaning is effective against infection between different rooms. It insists that ventilation systems are not a source of contamination if guidelines for heat recovery and recycling are followed. Viruses attached to small particles are not easily deposited in ventilation ducts and are usually transmitted through aircurrents anyway. Therefore, there is no need to change the cleaning and maintenance procedures for regular pipes.


REHVA represents more than 120,000 HVAC designers, architectural service engineers, technicians and experts from 27 European countries.


Knowledge about viruses is constantly updated, so REHVA thinks this can be considered a temporary guide. New evidence and information can be supplemented when the file is available.


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