UAE: Can coronavirus spread through air-conditioning vents?

Dubai: As offices resume functioning from their premises and more employees return to work, the question everyone is asking is whether COVID-19 can spread through air-conditioners, especially in a closed loop environment?

Concerns over the issue have also come to the fore after the World Health Organisation (WHO) recently acknowledged that the SARS-COV virus’ ‘short-range aerosol transmission’ in crowded indoor spaces cannot be ruled out. The updated brief came three days after a group of 239 scientists from 32 countries published a commentary titled ‘It is Time to Address Airborne Transmission of COVID-19’.

There have been no instances of spread of COVID-19 in the UAE through AC ducts, but research elsewhere has proved that the virus can remain airborne for over eight hours, following which doctors have emphasised the need to stay protected from a possible threat of transmission. 

Dr Mohammad Rafique, pulmonologist and head of infectious diseases at Prime Hospital, said: “Normally if AC vents are high, the chances of aersolised virus particles rising to that height are minimal. But in smaller spaces where the vents are lower or a single ventilation unit is shared between rooms, there is a chance of the airborne particles to travel and contaminate.”

Air conditioners typically re-circulate the same air through the room, and there is a chance that the coronavirus droplets can be transmitted through a single vent or even within one room. Studies carried out in the US and China have shown that air-conditioning can blow coronavirus droplets farther than six feet.

In China, it was found that air-conditioning blew droplets around a restaurant, infecting 10 people. On board a cruise ship, the spread of COVID-19 in 700 of the 3,000 passengers and many more even after being quarantined was likely attributed to the spread of the virus through the common air-conditioning system.

Offices that share a beehive of ventilation systems also need to take extra care to ensure that any moisture droplets or aerosol droplets do not become the cause of potential transmission.

In fact, there have been instances where choir singing in churches, as also close interactions in gyms and restaurants, have been suspected of such transmissions in parts of the world.

Dr Mazen Zouwahyed, consultant pulmonologist at the American Hospital, Dubai, explained: “Studies indicate that it is possible that if multiple units in the building share the same ventilation system, the virus can travel from one room to another. It has also been found that sitting close to someone singing or sitting close to people on an aircraft where such people may be asymptomatic carriers can result in aerosolisaton of the virus and can remain suspended in the air for over eight hours.”

Dr Rafique explained how this threat can be minimised.

“Airborne transmission in offices can be controlled if the air filtration system is cleaned out regularly, there are separate exhausts for each section and fresh air is let into the circulation system from outside. We do this all the time as part of our infection control protocol in the hospital," he said.

"High Efficiency Particulate Filter for Allergens (HEPA) filters are used in hospitals to trap any contagious viruses, bacteria and fungi from circulating in the room. Besides installing air conditioners at a height, other precautions to be taken are social distancing, wearing of masks and frequent sanitisation of common spaces and air filter cleaning. These measures will ensure minimum contamination of inborne air,” explained Dr Rafique.

What are aerosolised droplets?

Aerosols are generated when individuals cough or sneeze, talk or sing. Tiny microorganisms from the oral cavity get trapped in water particles created through humidity and travel through common ventilation ducts as they get airborne and pose a risk of transmission. It has now been pointed out by researchers that COVID-19 virus particles can remain airborne for eight hours.

How offices can handle the airborne threat

• No overcrowding - employees can work in shifts or on alternative days

• Maintaining adequate social distancing between employees

• Ensuring employees wear face masks at all times and suitable eye gear

• Cleaning and servicing the filters more often to clear out any trapped pathogens, moulds and fungi

• Making sure the exhaust vents are clear and the entire office does not share the same ventilation system. In other words, ensuring each room has a separate exhaust

• Carrying out sanitisation of the office space regularly to prevent spread of any infection