Are air-purifiers a cult?

[lshrtwll]

About every two years someone convinces me that a certain type of air purifier will improve my minor allergies, I will sleep better, and I will remove particles from the crappy city air.  But every time I buy one, I don't really notice any difference in the air.  I've tried different brands (high-end/low-end).  Some of the higher end ones smell bad and the air seems worse, and give me a sore throat. Now I wonder if they are really mythical technology from companies that just want to sell me filter replacements (and you hope they don't stop making them).

Your thoughts?

btw-I live in a mild climate and don't want/need air-conditioning. I do like to keep windows open for fresh (? non-house) air to come in.

[reeshau]

I use Honeywell HEPA filters in our main living room and in my bedroom.  I have developed pretty strong allergies to some pollen and mold down here, and in September and February, I limit outside time and otherwise manage my exposure, among other things.  I have learned how to manage, and it has helped a lot.

I have washable filter, and you do need to clean them.  But it's not difficult, and not that often.  I leave them on pretty constantly, as mold in particular can happen after any rainy period.  But I wash them before and after the high seasons, and don't have to do much else, 3 years after I bought them.

I never used or needed them before we moved to Houston.

[Sibley]

It's a ymmv thing. Some situations, an air purifier absolutely will help. For others, not really. It's not a bad idea to get one and try it, see if it does help. But once you have done so, you know the answer. Unless something changes in the environment of course.

[cannotWAIT]

I don't know about your mild allergies but I live in wildfire country and can assure you that they are not mythical technology. There have been times when I couldn't see to the end of my block because of the dark brown smoke, but could breathe clean air inside my house thanks to my HEPA filters. They have become absolutely essential household equipment out here.

[Freedomin5]

I live in a city with occasional high pollution days. The filters absolutely make a difference. Thee have been days when the air pollution was so bad that spending time outside resulted in breathing difficulties and a migraine even with wearing an N95 mask, whereas staying indoors in a room with an air filter helped with migraines and breathing difficulties. Obviously, when the filter is turned on, you need to keep your windows shut so you’re not constantly letting dirty air in.

[Metalcat]

My Honeywell made a MASSIVE difference for me.

My city home is in an old highrise on a major city intersection. If the Honeywell is off, you can see the air absolutely filled with dust particles if you sit in front of a window. With it on, there's almost nothing.

And yes, it absolutely had a massive impact on my allergies. We run it on the allergy setting 24/7

[FINate]

Not a cult, but lots of deceptive marketing for the "high-end" products. Your sore throat is likely caused by "purifiers" that produce ozone. Ozone is a pollutant which is why it gives you a sore throat, but it breaks down odors so it makes a room smell fresh. Don't pump pollutants into your home!

An air purifier is a simple mechanical device: fan + filter. The key is a HEPA filter and adequate CFM for the living space. We run large Honeywell filters in the main living areas plus a smaller quieter Levoit in our bedroom. We run them 24/7 on the lowest setting and this makes a big difference for us.

But they aren't magic. If you're mostly leaving your windows open there's no way an air purifier will be able to keep up -- your inside air is exchanging with the outside air far too quickly.

[GilesMM]

We use these BlueAir contraptions in sleeping areas and they make a huge difference for assorted particulates, especially during wildfire season.

[curious_george]

I have serious allergies and my HEPA air filter saves me every year.

If I turn the purifier off my allergies will come back, and I know when the filters need replaced because my allergies will flare up. After I replace the filter my allergies go away again.

Just two days ago my allergies flared up, then I realized someone turned my purifier off. I tuned it back on again and my allergies went away the next day.

It has been a life changer for me, but in my experience any basic HEPA air purifier works for me (I've had various ones throughout my life). No need for anything fancy or expensive.

[lhamo]

We usually only used ours in Bejing when the AQI was over 250, or when our downstairs neighbor (who smoked) was home.  The smoke smell would typically abate in abotu 10-15 minutes.  I can't remember the brand we had -- we got a good deal on them when somebody in the expat community organized a bulk buy.

Shameless plug:  This company was started by one of my Fulbright grantees and some friends who wanted filters at a lower cost than were then available in China.  They started out with box fans with HEPA filters taped onto them.  Design has improved quite a lot since then!

https://smartairfilters.com/en/product-category/air-purifiers/

[Dee18]

I had similar experiences to yours over the years: Honeywell (most expensive one I ever bought didn’t seem to do anything), Coway (recommended by NYT wirecutter, was so noisy it went back), Blue Air smelled funny even after weeks of running. I finally bought a Levoit core 300S and it’s been so good in my bedroom that I bought a 400s for my open living/ dining area.  They help with my allergies and when I have people over for dinner I run them both in my dining area as filtration does reduce the chance of covid transmission.

[dcheesi]

My wife can always tell when the filters need cleaning, even before the nag light comes on. We have a cat and she's mildly allergic, and it definitely makes a difference for her.

We have a Levoit (older model) at home, so I can vouch for that one; however, it burns through filters fairly quickly, so it might not be the most frugal option.

We have a Coway in our other property; seems to work, but then the cat rarely visits so it has an easier job overall. It's quiet enough in low/eco mode, but it does get loud at higher speeds (when it detects a major AQ issue).

[mistymoney]

How are you expecting the filter to work with the windows open if the issue is dirty city air?

[SweatingInAR]

A homemade Corsi-Rosenthal box fan filter can be made with hardware-store furnace filters and a box fan. It's pretty hideous and loud, though. I store mine flat in a closet and then rebuild+tape it when the air quality outside is bad, or any other time we want cleaner air.

https://www.texairfilters.com/a-variation-on-the-box-fan-with-merv-13-filter-air-cleaner/

I agree with everyone else, though, you need to close the windows if you want an air purifier to do anything.

[neo von retorch]

A homemade Corsi-Rosenthal box fan filter can be made with hardware-store furnace filters and a box fan. It's pretty hideous and loud, though.

I made one last June during the wildfires using a $20 box fan from Home Depot. It was definitely louder than a $300 air purifier, but not too much louder than the Levoit 300, considering how much more air flow. (Even on LOW it could do a fantastic job on the main floor of our 2200 sq. ft. home.)

But also I ran out of one of my rolls of duct tape mid construction, so it was a mix of bright orange and gray duct tape. It was, indeed, hideous!! We followed the recommendation to use extra cardboard from the fan box to block off the front of the fan leaving only the circle where the blades move air - this made the overall contraption a good bit quieter (and more efficient.)

My wife got me an AirKnight air quality monitor for my birthday, so I was able to watch the PM2.5 / PM10 drop rapidly with the box running. Or walk outside during a smokey day and see super high readings.

[FireLane]

I have a HEPA filter (a Coway Airmega, if it matters) that I bought for my wife's sake. She has bad seasonal allergies, and it helps her on the worst pollen days. It doesn't completely cure her hay fever, but she says it makes a difference.

But it really proved its worth during the bad air days last summer when New York was hazed with smoke from Canadian wildfires. The EPA said the air was extremely polluted and unhealthy to breathe. We hunkered down at home and ran the filter at full blast for a few days. I never thought of it as a disaster-preparedness tool until then, but I was glad to have it.

[Kris]

We have had one for years, at my husband's decision, and until last year I would have said it wasn't really that worth it. But when the Canadian wildfire smoke last summer was really bad here, I noticed a huge difference in our bedroom at night compared to the rest of the house (we don't have central air). So I am now a convert.

[tygertygertyger]

We have had one for years, at my husband's decision, and until last year I would have said it wasn't really that worth it. But when the Canadian wildfire smoke last summer was really bad here, I noticed a huge difference in our bedroom at night compared to the rest of the house (we don't have central air). So I am now a convert.

One of us! One of us!

[BlueMR2]

2 best things I ever did for allergies:

1) Switch to a closed system HVAC where it runs all the time and you are not supposed to open the windows.  Has a large efficient filter and our total bills now are actually less than when I used to open windows and use the whole house fan 10 years ago!

2) Work from home, so I don't have to leave this environment and go out into allergy land.  So many days each year I'd be at work nearly useless from allergies (either because of being so miserable or if I took anything for them it'd knock me out so bad I could barely function).

[dcheesi]

My wife can always tell when the filters need cleaning, even before the nag light comes on. We have a cat and she's mildly allergic, and it definitely makes a difference for her.

We have a Levoit (older model) at home, so I can vouch for that one; however, it burns through filters fairly quickly, so it might not be the most frugal option.

We have a Coway in our other property; seems to work, but then the cat rarely visits so it has an easier job overall. It's quiet enough in low/eco mode, but it does get loud at higher speeds (when it detects a major AQ issue).

Update: the Levoit unit just croaked on us; in a matter of moments between turning it off to swap filters, and trying to turn it back on, the touch-button bar that includes the power button became completely unresponsive. The usual troubleshooting came up empty, and online reports aren't encouraging

Unfortunately, DW was already suffering due the state of the filters along with extended cat cuddle time today, so I had to rush-order the latest model from the same brand. I'd rather have gone with another Coway like the one in our other property, but it wouldn't have gotten here for a couple of days. So yes, we're very dependent on our air purifiers!

[crocheted_stache]

We have air filters basically for wildfire days. Mostly, I'd rather have windows open.

A basic air filter should push air through some kind of a filter medium, which should, in turn, collect particulate matter. The box fan plus furnace filter is not a bad substitute, but a purpose-built air filter will usually use a centrifugal blower for lower noise, higher capacity, and better efficiency. Check the price and policy for replacement filters before you commit to a subscription or sign up for years of $$$$ replacements. Do replace the filters when they need it. I go based on use rather than months, because I don't run them often. The other thing is to match capacity with volume of air in your house.

Do not use the "ionize" or ozone function if there is one, and do not pay extra for this function if you're selecting a filter device. (The Detail Geek, an auto detailer on YouTube, makes correct use of a standalone ozone generator by putting it in a car for several hours while he doesn't hang around, if there's a biohazard or odor situation. It's not something to leave cranking in your bedroom while you sleep there.) This video debunking the Himalayan salt lamp also shows an ozone generator and measures the results. https://youtu.be/ZQ--scjcAZ4?si=393QJUa65qtytH-J

I would also question the need for any kind of "smart" features. Mine is supposed to vary the speed based on measured air quality, but I think the "off, 3,2,1" control on my $25 box fan would be sufficient. I don't really need to be able to control it from my phone, either.