Common questions about COVID-19 and air conditioning and refrigeration systems

Given the current coronavirus (COVID-19) pandemic, people are understandably concerned about how the disease is spread and whether air conditioning, refrigeration or other related HVAC&R systems could play a role.

AIRAH has compiled some of the most frequently asked questions and will continue to update these as more information becomes available.

For HVAC&R specialists looking for more detailed technical information and guides, and for those wishing to access further resources, you can also refer to our coronavirus information page.

Can COVID-19 be transmitted through air conditioning systems?

At this stage, there is no evidence that COVID-19 can be spread through air conditioning systems. Please note, however, that organisations around the world are assessing ongoing research on the ways COVID-19 is spread and will continue to share updated findings.

According to the World Health Organization (WHO), studies to date suggest that the virus that causes COVID-19 is mainly transmitted through contact with respiratory droplets rather than through the air.

When someone with COVID-19 coughs, sneezes, talks or even exhales, these droplets land on nearby objects and surfaces. Other people can become infected with the virus by touching these objects or surfaces, then touching their eyes, nose or mouth.

People can also become infected with the virus if they directly inhale airborne droplets from a person with COVID-19 who has expelled the droplets from their mouth.

The WHO recommends staying more than one metre away from a person who is sick. Research shows that airborne droplets can travel much further than one metre so it’s important to be mindful of this when you are near other people. How far airborne droplets carrying the virus can travel depends on air movement but can be several meters.


What actions are required for workplace heating, ventilation and air conditioning (HVAC) systems?

Although there is currently no direct research that supports that SARS-CoV-2 can be transferred through workplace HVAC systems, there is similarly no research to say that it can’t. However, studies show that the virus can be carried some distance by airflows with lifetimes of 0.5 hours.

What we do know is that HVAC systems can help control the spread of the virus.

Some international studies have identified the likelihood that COVID-19 may be transmitted in very small airborne particles called aerosols and attached to dust particles. Increasing outdoor air ventilation, using initiatives such as economy cycles, can dilute these particles. Building owners and operators should seek qualified advice on increasing ventilation in existing systems.

In line with guidance from SafeWork NSW, AIRAH recommends that employers seek confirmation from their building owner that the air conditioning system is properly designed and maintained.

Also, keeping relative humidity between 40 and 60 per cent will create conditions that reduce the risk of infection through inhalation of airborne droplets carrying the virus. Research from the International Society of Indoor Air Quality and Climate (ISIAQ) shows that viruses survive better at increased humidity with 60 per cent active above 60 per cent relative humidity.

Low humidity in occupied buildings should be avoided as this can dry out the mucous membrane which is one of our primary means of defence. ISIAQ research shows that virus survival decreases with decreasing humidity.

There is no clear indication that special filters should be installed in offices and similar environments. AIRAH recommends seeking qualified advice that effective air filters have been selected and maintained appropriately.

The following interview with ASHRAE presidential member William Bahnfleth contains useful information about the effectiveness of filters, UV and other HVAC technologies in controlling COVID-19.

Please note that some ventilation systems, such as those in carparks, do not recirculate – all air is exhausted directly to the atmosphere. These systems are therefore highly unlikely to spread the virus unless they feed into nearby air intakes for other HVAC systems.


Do I need to disinfect my home air conditioner?

There is no indication at this stage that home air conditioning systems can spread the disease. Although AIRAH recommends regular maintenance and cleaning of air conditioning equipment, there is no special cleaning or disinfecting requirement because of the coronavirus.

If you suspect that the surface of an air conditioning unit has been affected – by someone coughing on it, for example – use a simple disinfectant similar to that recommended by the United States Environmental Protection Agency to clean the surface.

Can COVID-19 be spread via the water in my evaporative air conditioner?

Evaporative air conditioning systems use drinking water. According to the Water Services Association of Australia (WSAA), drinking water in Australia is high quality and is well treated. There is no evidence that drinking water will be affected by the COVID-19 virus or that it is transmitted by drinking water. Existing water treatment and disinfection processes, including use of chlorine, are effective in removing viruses from water supplies. The WSAA has developed a public fact sheet for customers around water and COVID-19.

Is food at risk of carrying COVID-19, including frozen food?

According to the Centres for Disease Control and Prevention (CDC), there is currently no evidence to support transmission of COVID-19 associated with food. It says that “there is likely very low risk of spread from food products or packaging that are shipped over a period of days or weeks at ambient, refrigerated, or frozen temperatures”.

The CDC says that before preparing or eating food it is important to always wash your hands with soap and water for 20 seconds for general food safety. It also recommends washing your hands throughout the day after blowing your nose, coughing or sneezing, or going to the bathroom.

How easily can coronavirus spread inside a plane?

According to the WHO, research shows there is “very little risk” of any communicable disease being transmitted on an aircraft. However, several air cabin services staff have been infected.

The risk is like that which you would face in any other public place.

This is no different from any other situation in which people are close to each other, such as on a train or bus or in a theatre.

But transmission of coronavirus can occur between passengers who are seated in the same immediate area of an aircraft.

The WHO said this could occur when an infected person coughed, sneezed or had direct contact with another person.

Health authorities advise passengers seated within two rows of a confirmed case of coronavirus to self-isolate and seek medical attention if symptoms present.


Do I need to wear a mask?

Both the WHO and Australia’s Department of Health say you do not need to wear a mask if you are healthy.

You should, however, wear one if you are taking care of a person with suspected COVID-19 or if you are coughing and sneezing.  


How long can the virus last on surfaces?

According to the WHO, coronaviruses (including preliminary information on the COVID-19 virus) may persist on surfaces for a few hours or up to several days. This may vary under different conditions (e.g. type of surface, temperature or humidity of the environment).

Recent information, reported in USA Today, has found that viable virus could be detected up to three hours later in the air, up to four hours on copper, up to 24 hours on cardboard, and up to two to three days on plastic and stainless steel. The study has not yet been peer-reviewed and has not been corroborated by the WHO or CDC.

The WHO recommends cleaning surfaces that may be affected then treating with simple disinfectant to destroy the virus and protect yourself and others. Wash your hands regularly with soap and water or an alcohol-based hand rub. Avoid touching your eyes, mouth, or nose.


Got a question?

Please send your HVAC&R related questions to airah@airah.org.au and we will work with our AIRAH subject matter experts to answer.