December 2018 – As I was walking home from the grocery store in the Montreal suburb of Longueuil in one of the first cold days of winter, I found myself choking on smoke.
I started looking around to see if there was a house fire that was not yet reported – only to discover several chimneys sending heavy smoke into an inversion layer. An inversion layer is a common climate occurrence where smoke doesn’t rise but is pushed back down to the ground. It was obvious that several neighbours had started up their wood burning fireplaces that were not very efficient, or they were burning very poor quality wood. I too have a no better than a moderately efficient fireplace insert and had already used it about a week before. No house was on fire, but I could barely breathe as I walked down the street. Only this year the total ban of inefficient wood burning appliances has gone into effect on the island of Montreal and here I was experiencing the public health reason for that ban.
SMOKE IN YOUR LUNGS
My wife had been complaining about bad air and trouble breathing so we had stopped using our own fireplace and started looking everywhere for mold. Now it occurred to me that this smell outdoors was exactly what she was complaining about indoors. Then it jumped to my mind that our whole house ventilation system was bringing that smoke right into the house and spreading it out to every room! I turned it off, and things got a little better.
BUT AIR EX-CHANGERS ARE SUPPOSED TO BE GOOD FOR YOUR HEALTH…
Part of my profession is developing healthy houses and I am a strong proponent of HRVs and ERVs as essential parts to a healthy house – but not when the outdoor air is worse than the indoor air. For years these devices have had filters to keep dust and bugs out of the system and recently I have seen some HEPA filters for them to help stop pollen – but I have not yet seen any serious effort to filter out smoke.
ACTIVATED CARBON FILTRATION
The most efficient odour filter is activated carbon. We often have small carbon filters in table top air cleaners and if you think back to days when bars were dark with cigarette smoke there was always a large machine on the ceiling with heavy duty carbon filters and negative ion generators to make the place supportable. It could be a great idea to put such a large carbon filter just after the HRV (to avoid the cold air freezing it) but before distribution around the house. That way it would both filter outdoor air, but re-filter indoor air when in “re circulation” mode. The most common operation of these units is 20 minutes of fresh air and 40 minutes of re-circulation. But I have not seen large activated carbon filters for whole house air change units. So I started to hunt.
WHERE ARE THEY HIDING IN THE MARKET PLACE?
Most large space carbon filters were self-contained, hanging from the ceiling and just like the table top air purifiers; they took air in one side and pushed it out the other side. That was fine for a bar, but I needed one that I could insert right in-line with the duct system. After a lot of frustration, even comments from some manufacturers that it would be a good idea but not yet available, I started to think outside of the box – who needed to clean odours out of air on an ongoing basis?
I stopped by my local hydroponics store – hydroponics being the science of growing food and herbs in indoor water tanks. Sure enough I had a whole range of choice in large space inline carbon filtration. The one that fit my needs of having a duct in one end and a duct out the other end had a brand name that fit its unique air filtration purpose: The Air Box Stealth Carbon Filter.
So first I had to measure how much this carbon filter would slow down the air in my air exchange system, throwing the input and output out of balance. It turned out to not be too bad, but bad enough that I couldn’t just adjust the balance with the built in HRV dampers. So I needed a quiet in-line fan with a good speed control to compensate for the drag on the input side.
I was lucky that I had (4) feet of duct from the machine to the first distribution branch taking input air all around the house. So about $500 later, I popped it out and inserted both the Air Box carbon filter and the in-line duct fan set to a moderate speed which just keeps the whole system balanced or slightly on the high side depending on the automatic speed changes in the HRV. This prevents a negative pressure in the house from drawing that wood burning smoke in through cracks in the walls – while filtering out what comes in through the ventilation intake.
DOES IT WORK?
The day after it started filtering all the incoming air, and re-filtering all the air in the house in re-circulation mode, my wife started breathing better. Now when we step out of the house on a cold evening, we really smell the smoke polluted neighbourhood – and just as soon as we walk back into the house, we take a deep breath of clean air. Yes, the world is standing on its head. I guess we will keep this device running like this at least until Longueuil implements the wood burning restrictions that are presently in force in Montreal.
Update Feb 2019: It has been in place for two months now. We have never had such good, clean air in the house. Because it works both in fresh air and re-circulation mode, it cleans out kitchen odors (and burning smells) very quickly. If the fireplace back drafts, the odor is gone within the hour. And strangely enough, much less dust is collecting on my return air grills but the air flow measures the same as before.
Update Feb 2020: – This is the second winter. I had the large replaceable carbon filter recharged with new carbon for this season. It is still working wonders for both indoor and outdoor odours.
I have always understood the scientific arguments for eliminating small particle pollution as a health measure, now I see it is directly connected to a serious public odour problem as well. Rather than “accepting” the Montreal legislation, I now am ready to actively support such legislation throughout urban Quebec.
Best of all, I have discovered a working solution for living alongside wood stoves. Years ago I had a TV viewer who had to sell their house in rural BC because of their neighbours wood smoke – they had refused to stop by buying a modern non-polluting stove. With the Air Box Carbon Filter solution, you can now keep that neighbours pollution out of your house even without their cooperation.
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Who Is Jon Eakes?
After over 38 years as a prime mover in the field of home renovation — from hosting the first national home renovation TV show in North America, to a diverse career in radio and TV broadcasting, to his industry-leading work with regulatory, corporate and government agencies — Jon Eakes is still most interested in spreading knowledge about ‘the important basics’ — the fine details (and sometimes extended discussion!) the other guys leave out. Jon helps homeowners and trains contractors.