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Is A DIY Air Purifier The Right Way To Clean Wildfire Smoke From Your Home's Indoor Air?

Unless you find an effective long-term solution to keeping wildfire smoke out of your house in the decades to come, you may face old age without a reliable means of maintaining good indoor air quality in your home. I'll explain why standalone air purifiers - DIY or store-bought - are not an effective long-term solution to addressing the wildfire smoke which will become more prevalent in the decades to come, and I'll explain the better solution.

Old Age and Respiratory Health

In our 20s through our 40s or 50s, the lungs of a healthy non-smoker are still reasonably well able to deal with minor amounts of airborne particulate pollution. With age, that resilience decreases; in areas with chronically high pollution, the well-being of the lungs - among other things - decreases more quickly. In our 70s or 80s, we typically will be more vulnerable to airborne particulates such as wildfire smoke. If smoke is accompanying a heatwave or other extreme heat event, we face a greater risk of death.

illustration of old man coughing

Smoke from wildfires over the past two summers has spread across North America regardless of where the fires have been. It's everywhere; not even McDonalds and Starbucks have that kind of spread. There's no reason to think that wildfires will diminish in either frequency or size, and higher average summer temperatures which create drier forests only increase the probability of fires starting.

How long is that little purifier you've added to your bedroom or living room going to hold up? How long do you want to be paying for (and be able to find) the expensive proprietary replacement filters? The Corsi-Rosenthal DIY filter box that was developed around 2019 and adapted in 2020 for East Coast residents dealing with the smoke from massive wildfires in California is effective - no questions about it (link). However, those fans aren't intended to run day and night for an extended period of time. The furnace filters that are taped to the box fan have to be replaced after a while as well. For limited-time smoke events, these devices are great.

Wildfires are the New Normal

The problem is that wildfire smoke is becoming chronic. Twenty years ago, how much of a typical summer was filled with dangerous levels of wildfire smoke? I don't remember any.

2018 - California wildfires. 2019 - Siberia wildfires. 2020 - Australia wildfires. 2021 - Russia wildfires. 2022 - Oregon wildfires. It's 2023; wildfires got an early start and have over two months saturated most provinces. Much of North America is still blanketed in smoke, and wildfire season has only just started. Obviously, I'm cherry-picking a bit, but the worst fires in the 21st century according to Wikipedia are in the past ten years, and people across North America have been struggling with - and dying from (link) - air quality worse than that in New Delhi or Beijing.

realistic illustration of an exaggerated globe covered in smoke or dirty clouds

If you live in British Columbia, you've faced wildfire smoke. You will face it again when you're old. Heck, you're going to face it yet again this summer. Your homemade air purifier is not the answer. I'm a Certified Passive House Designer, so you may expect me to say that a HRV or ERV is the answer. IT ISN'T. Wait, what?

No - a HRV or ERV *combined with airtight walls, roof, floor, windows, and doors* is the best solution for keeping the air in your home free of wildfire smoke.

#1 The HRV or ERV

You may not be familiar with HRVs or ERVs. My article "Breathing Better and Saving Money With A Heat Recovery Ventilator (HRV)" explains what they are and how they work fairly well. In short, they're like fans that simultaneously pull in fresh air from outdoors and blow out stale, dirty air from indoors. Unlike a Corsi-Rosenthal box or a sophisticated air purifier, this equipment provides clean air to ALL spaces in the home and is designed to run continuously for decades.

However, they function effectively only if all the air into and out of your house is going through the HRV/ERV except for when you open your window or door. The problem in most buildings is that a large amount of air finds its way through your walls, roof, or through poor seals or joints around your windows and doors.

rendering of an airlock door into a very large piece of equipment

#2 Airtightness

The damage caused by air leakage is explained in the article "Is Your Home Slowly Killing You?", but if outdoor air is bypassing your HRV/ERV, then so is smoke from wildfires. The first tactic to cut down on leakage is to change the layer responsible - the air barrier. My article "Better Indoor Air Quality Using Better Air Barriers" explains these membranes in more detail, but most of them are basically sophisticated self-adhesive synthetic fabrics.

The second tactic is to improve the seals around the doors and windows - just like you were taught in the 70s and 80s during the oil crisis when people thought there wouldn't be enough energy to go around. Sealants, gaskets, and replacement seals may be enough, but you may need to replace the windows and doors themselves depending on their age and specifications.

comical rendering of a superhero protecting a window

If you want to use the analogy of a nightclub, the HRV/ERV is like the bouncer and the air barrier is like the doorman. If the doorman is letting in troublemakers, the bouncer can't keep things under control.

Imagine you're 75 and enjoying an afternoon nap at home. It's late summer, and forest fires near Squamish are covering your city in a nasty grey pall. Your home has a great air barrier and is super airtight though, and your HRV is scrubbing every cubic metre of air coming into your home. You can sleep easy and wake up refreshed.

simulated rendering of a cute old man napping peacefully in his bed in the glow of the world outside on fire

On the other hand, if you stick to your little purifier, you're 75 and they don't make filters for it anymore. Or, you don't have the patience and energy for reassembling another DIY box fan filter kit. You go lay down for your nap, but you can't get to sleep because the haze that's gotten into the house has put you into a coughing fit.

So how well would you say your current house is prepared to deal with worsening conditions? You can download my free Home Performance Self-Assessment and find out how your home scores.

If you've decided that you're not willing to gamble your future health on your home's current capabilities and you want to look at making some changes to your house, book a free 30-minute Diagnostic Session with me in which we'll determine if you're ready to evaluate your options for keeping yourself and your family safe from potentially decades of wildfire smoke.


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