Concerns over the safety of fans began after a Chinese study suggested that air conditioning in a restaurant in Canton may have helped to spread the virus between customers, and another study of 318 clusters in 120 towns found that “sharing a space indoors [with others] is a major infection risk”.
The World Health Organisation (WHO) has repeatedly said that while the virus can theoretically spread in the air, “studies so far suggest that the virus that causes Covid-19 is mainly spread through contact with respiratory droplets, rather than in the air.”
This means that the virus is mainly thought to be contained in droplets from other people’s cough or sneezes, which spread 1-2 metres in front of them, and then fall onto surrounding objects - such as tables - rather than hanging in the air.
Fans are only likely to “spread” the virus, in this case, if they are directly and strongly positioned next to someone as they sneeze or cough, and others are “in the way” of the air stream. Having air conditioning on - to cool a room overall - is therefore unlikely to spread the virus directly, studies so far suggest.
Read more: Covid-19: How to stay healthy this summer in France
New evidence, conflicting studies
But in recent days new studies have led the WHO to acknowledge that there may be evidence that the coronavirus can be spread by particles suspended in the air.
As the BBC reported today: “An open letter [to the WHO] from more than 200 scientists has accused the WHO of underestimating the possibility of airborne transmission.”
Jose Jimenez, a chemist at the University of Colorado who signed the open letter along with 238 other scientists, told newswire Reuters: ”This is not an attack on the WHO [but] we wanted them to acknowledge the evidence.”
Benedetta Allegranzi, the WHO's technical lead for infection prevention and control, said that evidence emerging of airborne transmission of the coronavirus in the "crowded, closed, poorly ventilated settings that have been described, cannot be ruled out".
And on June 22, the European Centre for Disease Prevention and Control (ECDC) said that even though the risk is limited, "the air flow generated by air conditioning units can facilitate the spread of droplets excreted by infected persons over longer distances in indoor spaces".
The ECDC also said: "Ventilation/air conditioning systems can play a complementary role in reducing transmission by increasing the rate of air exchange.”
Overall, the view is that spaces must be regularly well-ventilated with fresh air, but that strong air flow may spread droplets in some circumstances.
Current recommendations in France
In France, the health minister cited the WHO, and said: “To our current knowledge, it is not possible to offer [definite] recommendations linked to the risk of contamination by outside air.”
Yet health authorities have issued some suggestions on the subject of ventilation and air conditioning during the time of Covid-19, based on advice from public health council the Haut Conseil de la Santé Publique (HCSP) on April 24, 2020.
Recommendations include:
Fans
- Open windows and air out all rooms for at least 10-15 minutes twice a day, whether the room has fans / air conditioning or not
- Avoid using individual fans if there are other people in the room with you, especially if the room is small
- Turn off any fans if/when people from outside your household enter the room or approach you
Air conditioning units
- Open windows and air out all rooms for at least 10-15 minutes twice a day, whether the room has fans / air conditioning or not
- If you use your car, also leave the doors and/or windows open to air that out too
- Avoid recycling old air, and instead make sure your system brings in new air from outside
- If your system or location does not allow new air to be brought in, instead try to run your fan on low, and clean any filters at least once a week
- Check that openings are not obstructed - such as windows
- Check that your air conditioner is working well by placing a bit of paper in front of the vents - if the paper moves then the air is circulating
- Turn up the air conditioner when the area is unoccupied (lunch break, for example)
- Clean the air conditioning grilles and filters with soapy water at least every two weeks
Violaine Ohl-Gasteau, air quality filtration and purification manager for the French association of air-handling, cooling, heating and refrigeration industries, Uniclima, called for people to apply “common sense”, and told news website Actu.fr: “We should be avoiding big air movements. We don’t see air, but renewing it in buildings is essential. A building must breathe, to avoid mould, for example.”
Shops, offices, planes, trains
Shops and offices should adhere to these recommendations as much as possible, and avoid circulating old air.
Aeroplanes have their own air filters, often using the same filters (High-Efficiency Particulate Air, HEPA filters) as those used in healthcare establishments.
Train air systems depend on the type of train, but TGVs, for example, bring in new air (except when the train is in a tunnel), and so should be relatively safe.
SNCF says that air in its trains is “spread from bottom to top” and “entirely renewed every nine minutes in TGVs” and “every five to eight minutes in other rail models”.
In the metro, diffusers are often placed on the ceiling of trains to renew the air and ensure ventilation.
Covid-19 and self-isolating patients
The recommendations are stricter for individuals who suspect they have - or have tested positive for - Covid-19.
The HCSP said: “Someone with symptoms [or who has the virus] should be isolated in a separate room pending medical advice. In individual cases, meaning someone who is alone in a room without exterior contact, using a fan or air conditioner is no problem, from the point of view of spreading SARS-Cov-2, all the while checking that the air is regularly renewed.”
This means that even if you are using an air conditioner or fan, and self-isolating, you should still aerate the room by opening windows for at least 10-15 minutes twice a day.
Physical distancing and hygiene measures - such as regular hand washing, safe disposal of tissues, and thorough cleaning of surfaces - should be maintained throughout, in all situations.
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