Dear Urbaneer: Can I Catch COVID-19 From HVAC Systems?

COVID-19 & Toronto Real Estate, Dear Urbaneer, Healthy Home

Welcome to this month’s installment of Dear Urbaneer, where I take the opportunity to respond to one of my clients’ real estate queries. Last week, shortly after I posted my piece exploring How COVID-19 Will Likely Change How We Design Our Homes, I received a concerned email from a client who works in one of the corporate office towers in the Financial District. Although she is currently working from home, she is worried about the health risks she might face returning to her employment in one of the high-density skyscrapers. While she has reconciled the likelihood that elevators floor stops may be scheduled, employees may work on different days or be split into different time shifts, what’s most disconcerting to her is the risks that the heating, ventilation and air conditioning systems (HVAC systems) in her workplace may play in the spread of COVID-19.



Dear Urbaneer:

With the heat of summer in full swing and the AC cranked up to high in my home, it got me thinking that when I return to working in my corporate office in one of Toronto’s taller financial towers, I might be facing a high risk of exposure to COVID-19 if it is spread by airborne transmission through the building’s HVAC system? Is that a valid concern? One of my friends lives in a condo high-rise and she said her building has a central air chiller that cools everyones units. Can singular ventilation systems potentially contribute to the spreading of the disease in high density buildings?


Stay Cool, Stay Healthy




Dear Stay Cool:

Great question and one I’ve been hearing a lot of buzz around lately.

As I’ve written about before in my Healthy Home Series, our homes play a pivotal role in our physical, emotional, mental and spiritual health. And in today’s corporate rat race, the long hours career-pathers spend at their work environment, may mean they’re at work as much as they’re at home. In the past I’ve written about residing near power linesliving with asbestos, and what you need to know about household mold – which are also potential concerns in our daily work space! I’ve also written about Sick Building Sydrome, a phenomenon where the building’s engineering design, air ventilation systems, finishing materials and maintenance products can contribute to the creation of a ‘chemical soup’ that gets recycled through a building’s HVAC, causing people to fall ill. 

Just recently there was a COVID-19 outbreak in a Calgary condominium building, which the Province of Alberta is monitoring. The Calgary Herald reported that the cause is not yet determined, but they suspect high-touch surfaces may have played a role, along with the fact that there were AirBnb units in the building that saw steady traffic from travellers.

Returning to your question, we should discuss the theories around the transmission of COVID-19 through HVAC or air conditioner units. While there is still much we don’t know about COVID-19 and its behaviours, and there has yet to be conclusive scientific evidence to suggest that the virus does indeed spread through ventilation systems, there are a number of professionals and groups that feel that these mechanical systems could potentially play a role in airborne transmission.

Let’s first take a look at what we do know about how COVID-19 spreads, before delving into how mechanical systems could theoretically play a role in that transmission, and the ways in which you can protect yourself if you are concerned.




The Spread Of COVID-19

It has been determined that COVID-19 is transferred from person to person when an infected person sneezes or coughs; they project droplets into the air which then make contact with people and surfaces. The droplets are relatively heavy, and tend to fall to the ground within a 6-ft circumference, which is why this is the recommended measure for physical distancing.

If they contact another person before reaching the ground, these virulent droplets can enter via the nose, mouth, or eyes. It can be spread from an infected person’s hand as well if they coughed or sneezed virulent droplets on to their hand and then touched other people or common surfaces.

Challengingly, we now know that the virus can live for an extended period of time on surfaces (up to 28 days!). If you touch an infected surface (like a door handle), you can become infected by then touching your eyes/mouth/nose, as well as pass it to other surfaces and people. This is why it’s so important to frequently wash your hands often and avoid touching your face, but even more crucial to sneeze and cough into your arm, and stop the droplets from being expelled into the air in the first place.

This ‘shield’ technique is the idea behind the recommendation to wear a non-medical face covering. They won’t necessarily protect you from the virus, but masks can prevent infected droplets from escaping to infect others – especially if you are unaware or asymptomatic.



*Image courtesy of


COVID-19 And Airborne Transmission?

There is some dissension amongst experts surrounding whether or not (or the degree to which) COVID-19 spreads through airborne transmission.

There is a growing school of thought that believes that airborne transmission could indeed play a role in the spread of the virus, which was why HVAC, air conditioners and other ‘forced’ air systems were immediately flagged for further research. There is yet to be conclusive evidence to support this theory, however there are some thought-provoking case studies.

Essentially, ‘airborne transmission’ of a disease occurs when smaller, evaporated droplets are suspended in the air, or transform into dust particles which are spread on air currents and inhaled. I like this article by, titled, “Is The Coronavirus Airborne? Experts Can’t Agree.”

There are two studies (of many) that I want to recommend. The first study is from the New England Journal of Medicine, and it discusses ‘aerosol particles’ which are too small (micron range) to settle because of gravity; they are carried on air currents and dispersed by turbulence, thus giving them a longer reach. Can you imagine these particles being propelled through a building’s HVAC system – whether that be for living or working – where one system distributes air through multiple vents delivered to every otherwise self-contained space?

The second study is from National Institutes Of Health (PMC), and points to lessons learned from SARS, similarities between SARS and COVID-19, and, given the comparison, the likelihood of COVID-19 airborne transmission.

ASHRE  (American Society of Heating, Refrigerating and Air-Conditioning Engineer) recently released a statement saying that there is sufficient evidence to determine thattransmission of SARS-CoV-2 through the air is sufficiently likely, that airborne exposure to the virus should be controlled. Changes to building operations, including the operation of heating, ventilating, and air-conditioning systems, can reduce airborne exposures.

The consensus between medical and scientific bodies is that there is indeed a possibility that airborne transmission exists with COVID-19. And, given the enormous impact that COVID-19 has already had on our lives, on our health, and on our economies, all agree that it is worth exploring and investigating further.



*Image courtesy of CDC


Airborne Transmission Possible Case Studies

An event that occurred in early 2020 in a restaurant in Guangzhou, China has piqued the curiosity of many scientists.

10 cases of COVID-10 were tracked to an air-conditioned restaurant. These 10 cases were spread across three different families, and researchers believe the link in this outbreak was the location of these diners in the dining room and the air conditioning unit. No one else in the restaurant got infected, including servers and other people in close proximity.

One family (Family A) had just arrived from Wuhan, China, at the time the epicentre of the outbreak, carrying the virus into the restaurant with them. The two other families (Family B and Family C) sat at two neighbouring tables. Shortly after dining at the restaurant, members of the family that had travelled to Wuhan began exhibiting symptoms. Days after that, members of the other two families that had sat at the neighbouring tables began exhibiting symptoms.

The kicker? The only known exposure that Families B and C had had with the virus was being present in the same restaurant as Family A. But the puzzle here was that these three families were not in close physical proximity to transmit the virus as we would have expected, based on what we know about transmission.

However, the air conditioning unit was positioned over the table that Family C was sitting at. It is suspected that the force of the air flow from the air conditioning unit may have pushed the air between the tables, acting as a conduit for droplets are aeresol particles carrying the virus.

The CDC wrote a paper on this incident, using its findings to encourage restaurants to place tables further apart and make improvements to ventilation systems to curb the spread of the disease, titled, “COVID-19 Outbreak Associated with Air Conditioning In Restaurant, Guangzhou, China, 2020” Follow the link for the full story, plus some intriguing diagrams  and visuals. It reminds me of those murder mystery puzzles or games. “She couldn’t have done it – she was in the library at the time!”

Comparably, there were numerous cases reported on the Diamond Princess, the cruise ship that was quarantined for weeks in early 2020. Cruise passengers were confined to their cabins for an extended period of time, but those who still became ill may have contracted the virus through the air ducts. It wouldn’t take much, given those tight quarters.

Two great supplementary reads about the cruise ship are “Transmission Routes Of Covid-19 Virus In The Diamond Princess Cruise Ship” from MedRxiv, and “How Coronavirus Raced Through Quarantined Cruise Ship” by




Why Air Conditioners Could Be Problematic

The reason that some experts are concerned about air conditioning systems and the spread of COVID -19 has much to do with the way that air conditioning works. An air conditioner moves air around very quickly, removing humidity from the air, which is how it creates the cool air. And an air conditioner essentially moves recycled air through an area with force, theoretically giving infectious droplets the ability to travel further and for longer than they would on their own – which is what is possibly what happened at the incident in the restaurant in Guangzhou.

When a person coughs or sneezes and produces droplets, the droplets are usually bigger in size, meaning that they will fall to the ground within a relatively close area around a person; with the humidity being removed from air particles in as they travel the coils of an air conditioner, they become smaller. Moisture weighs droplets down, and lighter droplets might become more nimble. If they are virulent, they would pose the risk of airborne transmission, according to some experts (although it is important to note here that there are still a number of medical groups and experts who feel that COVID-19 isn’t spread at all as an airborne disease). 

If you took a look at the research surrounding the incident in Guangzhou, it seemingly shows transmission could potentially have multiple avenues.

So, is running your HVAC system really that risky? Experts feel that air conditioning within a single family residence is fairly safe, as you would typically be exposed to other people that live in the home already – and that the air conditioner wouldn’t necessarily exacerbate the speed and spread of the virus.

Similarly, as air moves through a large ventilation system – say, in a shared apartment building, workplace, or condo building – particles become smaller and as long as the system is efficient in cleaning the air, most potentially harmful air particles would become trapped. That said, due to the complexity and diversity of buildings types, sizes, construction styles, HVAC system components, and other building features, in addition to the fact that highrise office towers can be as old as fifty years and condos as old as forty, it’s likely almost every building that has been constructed over the past half a century has its own unique factors that contribute or limit the possibility of airborn transmission. Or am I being alarmist?

More on this in the ABC10 article, “Can Coronavirus Spread In Shared Air Conditioner Systems In Apartments?”




Transmission Of Disease Through HVAC Or An Air Conditioning Unit Is Nothing New

While the jury is out conclusively on whether or not COVID could be spread through airborne transmission, via an air conditioner/HVAC unit, the consensus is that it is documented that filtration and comfort systems do play a role in pushing other viruses through the air.

Legionnaires disease is generally contracted from inhaling Legionella bacteria. It causes pneumonia or lung inflammation. Several outbreaks of Legionnaires disease have been linked to air conditioning and cooling towers. Legionnaires disease grows in water, and the cooling towers in commercial air conditioners have been known to breed the bacteria and serve as a conduit to disperse it through large buildings.

In Toronto in 2005, an outbreak at a nursing home caused 21 deaths and sickened 127 people sick, linked to contaminated cooling towers. In 2012 in Quebec City, 13 people died and nearly 170 people fell ill as the result of an outbreak of Legionnaires disease linked back to the air conditioning. – CBC  Here is the information that was posted on “Legionella In Heating, Ventilation And Air Conditioning Systems”




Research Is Underway

Knowing what could potentially be at stake, there are groups that feel a call to action to determine the real risks. A Canadian study is underway to determine how HVAC systems in larger buildings could play an additional role in stemming the spread of disease (following under the same category as handwashing, physical distances, and mask wearing) as a “non-pharmaceutical” intervention.

They hope to complete the study by 2021.

In this release by the Canada Institutes of Health Research, Dr. Lexuan Zhong, the leader of the study says, “This work has the potential to impact millions of people living and working in high-occupancy structures… The spread of airborne infections in these types of enclosed spaces can have rapid, extensive, and detrimental consequences. Non-pharmaceutical interventions, such as those related to mechanical ventilation systems in buildings, could be a critical way to contain the current pandemic—or to mitigate outbreaks in the future.”

Here’s a deeper dive into some research in progress:  “COVID-19 Can Be Spread By Building Ventilation, Argue Canadian Researchers Working On An HVAC Fix”  [ -National Post ]  and “Can COVID-19 Spread Through HVAC Systems? Canadian Researchers Seek To Find Out.”  [ – Global News ]




 How To Protect Yourself

Although the consensus is that the disease itself isn’t airborne, but theoretically could be propelled by the force and the mechanisms of an air conditioning system, having good ventilation can assist in protecting from spread of the disease. Cleaning the air you breathe would fall under the same preventative category that hand washing, maintaining distance and wearing a mask does.

Having proper ventilation will reduce the likelihood of infected droplets going through the air. Being able to have fresh air coming into a space will reduce the concentration of droplets that might carry the virus, reducing the risk of contracting the disease. Theoretically, opening a window or a door is the way to accomplish that.

Admittedly, that isn’t always possible – especially in commercial buildings (the restaurant in question in Ganhzgao didn’t have any windows, for example). As such, it is advisable to have HEPA filters on your HVAC system to improve the air quality in your home, including potentially removing COVID particulates from the air – along with other impurities. If you live in a condo or apartment building, or are worried about air quality in your workplace, having a portable air filter in the room with you can be helpful as well. Maintaining your home at a higher level of humidity may assist as well, because it would make droplets larger and slower, less able to spread. Another trick is to install UV light fixtures!

So, the long answer to your question is this. An HVAC system likely won’t cause the spread of COVID-19, but theoretically could participate in it. The best way to stay safe is to engage in a multi-step protection plan that includes reducing the existence of those infected droplets at all into the air – like handwashing and wearing a mask.


Want to learn more? Check out these articles:

• Can Air Conditioning Spread the Coronavirus? Why Experts Are Concerned About Public Spaces  [ -GoodHousekeeping ]

• Can My Fan Or Air Conditioner Spread Coronavirus? Your COVID-19 Questions Answered  [ -CBC ]

• 2019 Novel Coronavirus (COVID-19) Pandemic: Built Environment Considerations to Reduce Transmission  [ -American Society For Microbiology ]


At Urbaneer, we are invested in your health and happiness while at home, and at work (or shall we say Work From Home), which is why we take such a comprehensive approach to finding you the perfect dwell. We’re here to help!



***ADDENDUM November 2, 2020 ***

We knew it!! COVID-19 brings ‘connection between the built environment and health’ back into focus, says the CBC:  “How the pandemic has put building design and ventilation back into the public health conversation.” Check out our blog here from June: “How COVID-19 Will Likely Change How We Design Our Homes



Here are our posts sharing how COVID-19 is impacting Torontonians with real estate:


Demand For ‘Forever Homes’ In Toronto’s Downtown Family Neighbourhoods Persists Despite COVID-19

With COVID-19 Outbreaks In Long-Term Care Facilities, Is Multi-Generational Housing Better?

Healthy Home: The Irony Of Navigating COVID-19 On The 50th Anniversary Of Earth Day

Assess Your Risk: Buying & Selling Toronto Real Estate During The COVID-19 Pandemic

The Role Of Fiscal Stimulus During COVID-19 And Toronto Real Estate

Access To Support & City Offices During COVID-19 For Toronto Real Estate

March 2020 Toronto Regional Real Estate Statistics: Before & After COVID-19 Arrived

How Canada’s Big Banks Are Responding To The COVID-19 Pandemic Panic

Consider A Mini-Home-Makeover To Feel More Comfortable During Self-Isolation With COVID-19





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Thanks for reading!


-The Urbaneer Team

Steven Fudge, Sales Representative
& The Innovative Urbaneer Team
Bosley Real Estate Ltd., Brokerage – (416) 322-8000

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