As more and more people get locked inside their homes for three weeks or more to limit the transmission of the global coronavirus pandemic, and the onset of the summer season driving up temperatures – an unlikely question asked by some of our customers has been – does the usage of air conditioners increase the risk of spreading coronavirus?
To answer that and also put some myths aside with some facts, the European Federation of HVAC associations, REHVA headquartered in Belgium has now published an advisory based on current best knowledge as contained in the World Health Organisation document. indicating that AC and humidification systems have no practical effect on the transmission of the virus.
This was recently backed up by research of the UK’s F-gas certification body – REFCOM, stating that there is still no evidence of air conditioning or ventilation systems contributing to the spread of the coronavirus.
“It is really important to reconfirm that, at this stage, there is still no evidence that air conditioning or ventilation systems are contributing to the spread of the virus” – Graeme Fox, Head of Refcom.
The REHVA document insists that heating and cooling systems can be operated normally as there are no direct implications on Covid-19 spread. Unlike some other viruses, SARS-CoV-2, the virus which causes the Covid-19 disease, is quite resistant to environmental changes and is susceptible only to high relative humidity above 80% and a temperature above 30˚C.
“This virus is not airborne in the same way as viruses that cause common cold and flu. It is just that if a person sneezes, a thick spray gets created — that is when a virus is in the air. But it does not float around in the air — it settles on surfaces and can stay there for a very long time” – Sambuddha Chaudhuri, Epidemiologist at the Indian Institute of Technology, Bombay.
TEMPERATURE & HUMIDITY
The document insists that humidification and air conditioning have no practical effect on transmission of the virus. Unlike some other viruses, SARS-CoV-2 is quite resistant to environmental changes and is susceptible only to high relative humidity above 80% and a temperature above 30˚C.
On being asked that if high temperatures in fan coil units can eliminate the virus, REHVA association suggests that to inactivate the virus, a temperature increase is needed up to 37˚C for one day and 56˚C for 30 minutes. For large central Fan Coil Units based systems it is recommended that with a safety margin consideration of 3-4˚C, it could be advisable to operate at 40˚C for one day and 60˚C for one hour. These temperatures apply mainly for the heat exchanger surfaces and not the filters where temperature is expected to remain at lower levels.
AIR RECIRCULATION
In duct based central air conditioning systems, the virus particles in return ducts can re-enter a space incase air handling units are equipped with recirculation sectors. So, it is recommended to avoid central recirculation during SARSCoV-2 episodes by closing the recirculation dampers.
When possible, it advises that decentralised systems such as fan coil units that use local recirculation, also should be turned off to avoid resuspension of virus particles at room level. Fan coil units have coarse filters which practically do not filter out particles with viruses. If not possible to turn off, these units are to be included into cleaning campaigns, because they might collect particles as any other surface in the room.
REHVA represents over 120,000 HVAC designers, building services engineers, technicians and experts across 27 European countries.
Knowledge of the virus is constantly being updated. This advisory may be complemented with new evidence and information when it becomes available.
To read the World Health Organisation document ‘Getting your workplace ready for COVID-19’ hit up this Link.
For more on REHVA check out their Website and future updates and documents can be found Here.
