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Discussion Starter #1
I'm looking to rent a condo or apartment (in a building with many occupants) but am concerned about air circulation and COVID-19. The scientific picture is not clear. Some sources say that building HVAC systems are not a significant COVID-19 threat, but I don't want to take any chances. Officials have been very slow catching on that COVID-19 is airborne.

The dangerous situation I want to avoid is where air flows from someone else's unit into the hallway, then into mine. I've previously been in apartments where I can smell someone else's cooking or cigarette smoke. Clearly, that also means that if they are coughing up a storm, those particles are coming into my home.

One "test" I have thought of is to walk around the building's hallways at 6 pm, smelling for odours or cooking. If I get whiffs of odours in hallways, it means air is flowing the wrong way. Do you think this is a good test?

Any other ideas on how to avoid buildings that have a hazardous kind of air flow, or bad recirculated air? Should I be avoiding all central heating where vents blow directly into the unit?
 

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Discussion Starter #2
And in case it helps, here are a few different things I've seen in buildings before. I just am not sure which are good, which are potentially dangerous.

Hallway pressure. Some buildings pressurize the corridors, keeping them at positive pressure, resulting in airflow into each unit. As far as I can tell, this is good. If working properly, it prevents air from inside a unit from spreading to others. Cooking smells and coughs stay inside each unit.

Central heating / forced air. The air is centrally heated and then blown out of vents into each unit. But could these vents also connect the air flows between units, resulting in contamination?

Radiators. Old fashioned fluid circulating through radiators will heat each unit, without blowing air around.

Other local heat. Instead of radiators or central heating, I've also seen electrical heating inside individual units.
 

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^^ Not sure how you can avoid the "free air all around us" or in your situation breathe in your neighbour's air other than wearing a mask inside to hopefully filter out some of the the dirt, bugs, et al.
 

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If you’re afraid to breath air that was breathed by others, there is only one solution...stop breathing. All air has been contaminated in your view.

btw, most apartments are heated with hot water radiators.
 

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If you’re afraid to breath air that was breathed by others, there is only one solution...stop breathing. All air has been contaminated in your view.

btw, most apartments are heated with hot water radiators.
I find the topic irrelevant. Covid19 is not known to be airborne, only droplet spread.

Your comment re apartments being mostly heated with hot water radiators is more interesting Just a Guy. That may be true in a given area or for apartments of a given age group but I don't think it can be said to be 'most' overall. Many places use electric baseboard heat for example in both apartments and houses. The downtown Toronto condo my brother used to live in had individual heat pumps. That building was put up in the 70s. I only expect to see hot water radiators in older buildings.

Our 2006 built condo in the Okanogan had a 'swamp cooler' roof mounted to cool hallways and common areas. Individual units had wall mounted air conditioners and electric baseboard heating. I don't think we can really say 'most' use one way or another unless we add a location and building age to the picture.
 

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Hot water heating is the one form of heating that I’ve seen in every province. The same cannot be said for any other heating system that I’ve seen. Yes, there are other forms of heating, but hot water is the most common one I’ve seen. Even new builds are getting hot water heating still, it’s not some abandoned technolog...it’s very efficient. Heck, even my house is heated that way.
 

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Discussion Starter #9
^^ Not sure how you can avoid the "free air all around us" or in your situation breathe in your neighbour's air other than wearing a mask inside to hopefully filter out some of the the dirt, bugs, et al.
Well, there are differences in how buildings manage their air and I'm wondering if some types are better than others. The one I mentioned with pressurized hallways involves, as far as I can tell, fresh air coming from outside. There is typically a unit at either the top or bottom of the building which takes in fresh air, and pressurizes the corridors. It sounds to me like this results in excellent air quality in the units.

Compare that to an apartment which allows air flow between units, so the air comes out of one unit, then goes into other units. This is unquestionably worse.... and it does happen in some buildings.

Not all buildings are the same. HVAC systems can be quite different, which is why I'm asking.
 

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Discussion Starter #10
Which sources say this?
Earlier, I found some articles that said "don't worry about it". They were taking the (early and outdated) position that COVID-19 does not spread through the air.

The more current scientific opinion is that airborne transmission is possible. I spent hours looking for articles about risk of spread inside apartments and condos, and found very little -- this is just not something that is well understood right now.

Here are some resources:


This article explains that many institutional HVAC systems (more like offices) are fundamentally air recirculation systems. It describes that viruses can move from one area to another, but thinks that the risk is reduced due to various factors (like some filtration). They give some recommendations on how the HVAC should be properly cleaned, filteres replaced, etc. They also mention that the filters used in typical HVAC are not good enough to stop viruses.

The professional body for heating & cooling has also released official statements on this topic:

Transmission 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.

Ventilation and filtration provided by heating, ventilating, and air-conditioning systems can reduce the airborne concentration of SARS-CoV-2 and thus the risk of transmission through the air.
My understanding is that they are informing buildings that they should increase the % ventilation (fresh air intake, as opposed to recirculated air) and make sure filters are in good shape.


This article also cites experts who believe there is airborne transmission. The following is the only solid advice I have found about my question

Fortunately, there’s a pretty simple solution, one Allen said would make sense even if we weren’t in the midst of a pandemic. “We can put in high-efficiency filters for the recirculated air, which can be really effective at capturing airborne particles,” he said.

If you live in a mechanically ventilated building, Allen suggested asking the landlord or manager about the HVAC system: Does it bring in fresh outdoor air? If air is being recirculated throughout the building, how is it being handled? “Make sure they have high-efficiency filters, a MERV 13 or greater,” he added, referring to the rating system for air filters.
This goes back to my earlier point, and something that Just a Guy doesn't seem to understand even though he's a real estate pro. Not every building has the same kind of air flow and HVAC systems. Some include more fresh outdoor air; others do more recirculation.

Some buildings may not circulate air at all. Perhaps these ones are the safest buildings?

Other things people can do are, as sags said, open the windows to get some fresh air yourself. You can also use portable HEPA air filters inside rooms.

From all my research, it seems that the key danger in apartments and condos is recirculated air. Not every building does this, but some do. So the questions are: how much fresh air is brought in? How does the building handle recirculated air?
 

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Discussion Starter #11
I phoned the property manager for my last apartment building and asked some of these questions. Here is what I found out.

Their building does pressurize the hallways. I asked: do they recirculate air, or is that fresh air? The manager said that the air blowing into the hallways is fresh, taken from outside.

For individual apartments, it's electrical heating and air remains local to each unit. Air does not recirculate.

I think this ^ is an example of a pretty safe scenario.
 

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Discussion Starter #12
And here's another example I heard from a friend. He lives in a townhouse kind of building, where one physical house contains 6 separate rentals.

They have central heating & air, which blows air, but air is only recirculated within their own home. Air does not mix with the neighbours. This is also pretty safe, because you're only dealing with your own air... it's not broadly recirculated.
 

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I doubt the risk would be very high. The smell from cooking and smoking is a bit different, because these are gases that linger in the air for longer, until they get diffused. I find the smell of MJ especially sticky and permeating in apartment buildings, seeping in from around the windows. But droplets eventually fall or evaporate. Unless there is a high concentration of droplets and strong movement of the air, the risk should be relatively small.
 

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Earlier, I found some articles that said "don't worry about it". They were taking the (early and outdated) position that COVID-19 does not spread through the air.

The more current scientific opinion is that airborne transmission is possible. I spent hours looking for articles about risk of spread inside apartments and condos, and found very little -- this is just not something that is well understood right now.
All the high level medical advice says airborne transmission is very low risk and close proximity only where droplets transfer. I mean if there was any serious airborne potential they would have had a 10m-50m buffer, not a 2m one. IMO, you're overthinking this but it's your call.
 

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Discussion Starter #17
I certainly hope that building air / HVAC is not a common transmission route. Note that the engineering association for heating/cooling does express concern, and says pretty clearly: "Transmission of SARS-CoV-2 through the air is sufficiently likely that airborne exposure to the virus should be controlled."

Yes, realistically I might not be able to do anything, other than keep windows open, or use a portable air filter. Over the years, I have used small HEPA filters in my apartment because it helps with dust and allergens, anyway.
 

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The system that sends air into the corridors that then flows under doors into apartment units is called makeup air, so named because it makes up for air that flows out of a unit through the range hood, bathroom fan and dryer vent. I think it is required by building code in newer buildings. There is positive pressure in the halls that also tends to keep airflow and smells from moving out of units into the corridor. Makeup air should be fresh, filtered and heated or cooled according to the season. It's cheaper to send makeup air through the corridors than to build fresh air ducts unto each unit. Positives are fresh air reduces incidence of condensation, mold, mildew and CO in units. Negatives are sometimes it does not work properly. The system may need balancing to ensure all floors get adequate air flow. If someone on the windward side of the building opens a window the breeze may blow in, reversing the air flow from the unit into the corridor, and people tend to open window when they cook or smoke, sometimes exacerbating the smell to other units. Some people don't like the draft from under the door, so they weather strip the door bottom, thus resulting in stale inside air.

Many newer buildings also have a self contained HVAC system, with a heat pump or gas furnace + AC unit that draws in air from inside the unit, filters & heats/cools it and sends it out through ducts in the unit. The advantage of this is each unit owner controls their own temperature with separate electricity and/or gas billing per unit thereby encouraging conservation. They can also upgrade the air filters in some systems if they want, especially those with allergies.

A lot of older buildings I have seen have wimpy make up air systems resulting in humidity, condensation and possibility of mold and mildew buildup. I am guessing that building code has increased fresh air requirements over the years.

Overall I think I prefer fresh constantly flowing air for a clean interior environment over the older systems, even if it means some (unknown) risk of a virus coming in from the corridor. The droplets that would carry the virus would have to move along the corridor, under a door, along the floor then up again to a surface or to the level of air you would be breathing. Sounds possible, but not super likely.
 

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Discussion Starter #20
Thanks GreatLaker, this is great info. Your description matches the system in the last building I stayed in: the makeup air is fresh air, and is constantly flowing from the hallway into the units. Given that this air is not recirculated, and is probably keeping each unit's air from spilling back to the hallway, to me it sounds like a pretty safe configuration.
 
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