♫ All I need is the air that I breath ... ♫
September 12, 2020 8:24 AM   Subscribe

My family lives in Vancouver. The air quality here is poor at the moment, because of nearby fires. The standard advice appears to be "Stay indoors, to avoid the smoke." This puzzle me: surely the air indoors comes in from the outside through the windows, so if the air outside is hazardous, the air indoors will be hazardous too, right? So we're thinking of buying air filters. But how many do we need?

My question is this. Suppose I buy a filter with an "operating area" of 300 square feet. Can I use it to purify the air in my entire 2000 sq ft house, by moving it from room to room? Or will I need multiple air purifiers?

Thank you in advance for your advice!
posted by HoraceH to Home & Garden (12 answers total) 2 users marked this as a favorite
 
I have an air filter, but other that that, I have no expertise in this area. The way I use my air filter is to carry it to whatever room I'm spending time in, i.e. bedroom, office etc. Close the door and run the air filter in that room. My filter has a digital read-out that shows what the air quality is. Once its been in a room for a bit it can get the air quality somewhat better (we have a lot of smoke from fires currently). Leaving the door open to the rest of the house makes the air quality in the room go down. So to sum up, an air filter that does 300 sq ft would not be able to filter your whole house at once.
posted by WalkerWestridge at 8:38 AM on September 12 [1 favorite]


My parents have been using HEPA filters (or something similar) in their HVAC system, and then just running the fans on indoor air. Supposedly these DIY filters also help quite a bit.
posted by pinochiette at 8:43 AM on September 12 [2 favorites]


Several fb posts have talked about cleaning and reinforcing home ventilation filters, running ac or heating fans just to filter the air, lots of comments on what stores have filters in stock. Also about wearing masks indoors. it's pollution, it's bad for you.
posted by theora55 at 8:44 AM on September 12 [1 favorite]


Also, to answer your question about windows, the idea is to keep the house as tightly sealed as possible- all windows shut, tape up gaps, etc.
posted by pinochiette at 8:44 AM on September 12 [2 favorites]


If you have HVAC in your place, you can turn on the fan run always. Then put filters into your HVAC unit. THe big ol square ones.

+1 for the DIY version as well, works great!
posted by bbqturtle at 8:44 AM on September 12 [1 favorite]


If you have a forced hot air furnace that allows for an air circulation function, you should replace your furnace filter (double checking to make sure they filter smoke particles) and just run that; halfway decent furnace filters screen out smoke particulates: this has helped a ton. If you can find HEPA filters (which are hard to come by in some areas right now), do that; they will also help filter viruses.

The DIY box fan/furnace filter combo also works, but not amazingly well. If you have box fans and are going to pick up some furnace filters, it can be a cheap, less than ideal but okay fix for knocking smoke particles out of a room.
posted by furnace.heart at 8:46 AM on September 12 [1 favorite]


This depends on the layout of your dwelling and how airtight it is. I have a "350sf" filter that's been doing a fine job of keeping my 1375sf house free of smoke -- but I'm on a single level, I put it in the central hallway, I keep my doors generally open to that hallway and I have very well-sealed windows and doors. My filter is one of those auto-detecting ones that spins up and down depending on pollutants, and it's spending 99% of its time on the lowest setting now (but it will freak out for a while if I open the front door, for example).

...the easiest answer of course is to buy one machine per room, but if you pause to consider your specific house you may be able to get by with substantially fewer.
posted by aramaic at 8:46 AM on September 12 [1 favorite]


We have a single filter (the same model that Wirecutter recommends) for our ~1100 square feet of living space. It has been keeping up adequately for the inside air quality but we are rigorous about keeping the doors and windows shut (meanwhile, outdoors is dim and yellow from the smoke; trees more than a couple of blocks away disappear like in heavy fog). If the smoke was much worse, though, I think we would need two filters since we can only seal things off so much.
posted by Dip Flash at 9:11 AM on September 12 [1 favorite]


We're just moving our filters to the rooms we're in, as others have said. Unfortunately our main floor is "open concept" so it's just not that pleasant to be in. The filter can only do so much. But in the bedrooms you can see the AQI drop within seconds when you switch the filter on. It seems most critical to cover all the rooms where people or animals sleep, not only because that's a long time but because you aren't awake to notice the air getting smokier.
posted by potrzebie at 9:34 AM on September 12 [1 favorite]


It may not help with the "whole home" picture but if you get a basic air purifier/fan (I got one online for $75 or so) you can at least keep one room clear, like your bedroom, where you spend a lot of time breathing. Seal that one off, run the purifier all the time, and it's your escape area.

I've also plugged gaps in our old apartment building's windows and doors so that there isn't a constant influx of smoky air from the outside and hallways. You can't get it to zero but what you really need to do is just keep it significantly lower than the surrounding air.
posted by BlackLeotardFront at 12:40 PM on September 12 [1 favorite]


That's a good question, HoraceH. If smoke were a gas like nitrogen, the concentration would be about the same inside and outside your house.

Instead, it's mainly a suspension of fine particles in a gas, and those particles have a tendency to precipitate out on surfaces, especially when they go through narrow, tortuous passages.
posted by jamjam at 1:21 PM on September 12 [1 favorite]


Thank you for your answers, everyone. I bought the largest air purifier I could find, and by moving it around the house I seem to be able to keep the air quality at an acceptable level.

Now I need to learn more about smoke diffusion ...
posted by HoraceH at 10:49 AM on September 14


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