Mike Mares on Health in Toronto...
Staying healthy in Toronto's polluted atmosphere: Information for asthmatics and other homeowners who want to clean up the air they breathe and stay healthy in the Southern Ontario air pollution belt; and for heating and cooling contractors who want to help them
by Mike Mares, Faculty of Medicine
Update, February 2006: Good news! We got an engineer involved, and the non-functioning system has been replaced with a VanEE (Venmar) unit that is a combined HRV and HEPA filter unit. Unlike the other models, this one is designed for installation in an apartment.
Evaluation, July 2008: We're glad we have the Venmar, but we wish it had more power--it's a bit small for a 1,000 square foot home. It does what they call one air change per hour (a bit less on regular speed, a bit more on boost). This is within the standards for a residence, but it can get stuffy, so when the outside air is reasonably good we sometimes open a window for a while. All of the incoming air that comes through the system is filtered; some of the recirculating air is filtered; we tried filtering it all, but that reduced the flow of air into the rooms to almost nothing.
Another problem is that much of the time we have the bathroom fan, the range hood, or the vent for the dryer on, and this unbalances the system, lowering the air pressure in the home to a point where some less pristine air from within the building is going to be drawn in at the front door (which we have weatherstripped to the nth degree), through any cracks around plumbing pipes (which we have sealed with polyfilla), light fixtures, etc. So again, if the outside air is not too bad, we open a window a couple of inches. (We find out how bad the air quality is by doing a search on Google for air quality Toronto.) For information about what an air cleaner cleans, and for further technical information, read on. We think a better design would have a larger air intake hole and a damper to shut off or reduce outgoing air when there is an exhaust fan on. We would also be interested in a non-HRV system in which the air comes in through the unit and exits through one of the existing exhaust fans, so that one exhaust fan is always on.
July 15, 2005
Smog warnings are issued when there are very high levels of one or both of the two contaminants that are the most severe health hazards and the greatest danger to the lives of asthma sufferers: ozone and small particulates. Both are prevalent in Toronto and throughout Southern Ontario.
Ozone is an unstable mollecule and is usually not a problem indoors; outdoors in the presence of certain pollutants it is continually produced, but this requires direct sunlight. (The half life is sometimes said to be half an hour, though it varies from seconds to days, depending on the conditions.) In any case, so far as we know there is no equipment available to break it down, other than in fish tanks. (So generally avoid electrostatic air cleaners, because they produce ozone. Photocopiers also produce it, some much more than others.)
Small particulates can be mechanically removed by a HEPA (very fine) filter. In a house it's usually easy: you run the incoming air through a HEPA filter unit connected to the furnace. You include a heat exchange to save on heating and cooling costs, and of course keep the windows closed. But in the area where we like to live, most of the houses are old with finished basements that are likely to conceal mould--another health hazard. So we investigated how we might run the incoming air through a HEPA filter in a condominium.
We had already found that it could not be done in the condominium in which we were living, as there was no central air circulating system. The only option would be free-standing air cleaners, which can keep the particulate level very low in a closed unventilated room, but cannot clean incoming air. Fresh air is important not only to supply oxygen and prevent the buildup of carbon dioxide and other gases given off by the human body, but also because furnishings, cleaning products and personal care products release air pollutants harmful to health. As one article on indoor air pollution put it, "even if you live downwind from the chemical factory, you are better off keeping your windows open". We have done a lot to minimize indoor air pollutants, but some are unavoidable. (If you want to know how to minimize indoor air pollutants, the Canada Mortgage and Housing website is a good source. Commercial cleaning products are generally to be avoided. Baking soda, soap and vinegar will do the regular cleaning jobs.)
So we looked for and found a condominium for sale with a heat pump and central air. We found a heating and cooling company that said they could bring the outside air in through a HEPA filter so that we could keep the windows closed and breathe good air low in small particulates. We bought the condominium, had the system installed, and ran into problems that we are still trying to get fixed. Unfortunately the company which did the installation has not co-operated in trying to find a solution, which is why we are still unable to use the system after more than a year. These are the problems:
The fan that forms part of the HEPA filter unit is not strong enough by itself to bring in any significant amount of air, so we have to leave the windows open and cannot use the system to clean incoming air.
We thought that this problem could be fixed by installing a booster fan and if necessary a bigger pipe--if it were not for the second problem. In designing the system, the company ignored the specifications of the heat pump into which the outside air was to be drawn (via the HEPA filter).
A condominium heat pump is a small affair which has to fit above the ceiling; it does not have room for sheet metal to keep water that condenses on the coils off the insulation (as is found in some commercial heat pumps). It is designed to take in indoor air, which is at about the same temperature as the heat pump. In warm weather (when outdoor air quality is typically at its worst) the warmer outdoor air, which is carrying more moisture than the cooled indoor air, will discharge the extra moisture on the coils in the heat pump if it is drawn directly through them. Thus there is a danger of water dripping from the coils, sitting on the insulation, and causing mould. (Mould triggers allergic responses in the 10% of the population with allergies, and some moulds are toxic to everybody. To clean the mould out would require replacing the heat pump and all the ductwork--for starters.) Provision should have been made to dehumidify the air before it reaches the heat pump. There were other problems.
Answer to an asthma sufferer who requested help in choosing a suitable condominium:
You need a place with a central air system and ducts. If there is already an HRV (heat recovery) system, check whether it has a HEPA filter, and if not, look into replacing it with one that does (such as the VanEE). If not, you need to be able to build something into a window to pipe the outdoor air into an HRV unit with a HEPA filter, and thence to the central air system. I would suggest you ask VanEE to suggest a contractor who can take a look at the feasibility in a place before you buy it. You want all the outside air and as much of the inside air as possible to go through the HRV unit. That of course will only remove small particulates, not other pollutants. You want to be able to have an air intake where the air is relatively clean, not near the laundry or parking lot.
One thing to note is that indoor air pollutants can be even worse than outdoor pollutants, so it is important to get a good seal around the door (unfortunately the halls are pressurized in apartment buildings) and to avoid carpet and floorings that emit toxins. If you have allergies it is important to have the right kind of bedding and maintain it in such a way that you are not breathing large quantities of dust mite detritus. Kitchen countertops are typically made of particle board which is fully exposed at the bottom. We replaced ours with new ones custom made from exterior plywood, which emits virtually no formaldehyde. Humidification and dehumidification is also an important and tricky issue. See the Central Mortgage and Housing website re indoor air quality. If you want to check whether your efforts to reduce dust mites and moulds have been successful, ASH Pest Management will check it for you and send you a report with control suggestions for a very modest fee. Their phone number is 519-542-5072.
Copyright © 2005 Mike Mares
Faculty of Medicine, University of Toronto, Kings College Circle, Toronto, ON M5S 1A8