Do they make a difference? Perhaps a placebo? A must have?
Genuinely interested if I'm missing out - For what it's worth I do live right on a main road in the UK, so I expect there is some level of pollution in the air.
I got the cheapest air purifier from Amazon and just put it on my bedside table. After one night my sore throat was gone.
As simple as these machines are, they do work.
I guessing that the benefits are less certain in more typical cases.
It’s a little hard to believe if you haven’t lived there recently, but basically the entire US west coast now has an annual fire season where you can expect at least several days of air quality in the “unhealthy” to “hazardous” range. AC (which does ~the same thing for air quality as a purifier) or a purifier is pretty much mandatory.
And healthy is something like <100
What doesn't work well for me is the auto mode, it barely does anything at less than 50µg/m^3, way too high even for the mediocre air in my area. So instead I use automation in their app to let it run at full speed for 30 or 60 minutes.
Purchase an air quality monitor, something like the Dylos DC1100. Then run a HEPA filter in a closed room for 30 minutes. It will remove almost all particulates! They work extremely well. Whether it "makes a difference" for your health is less clear.
I'd expect there are smaller / sleeker / more advanced monitors out now though. Generally speaking I think you want a laser detector instead of the cheaper infrared detectors.
HN's own https://news.ycombinator.com/user?id=ahaucnx has a company with a DIY version: https://news.ycombinator.com/item?id=27124671
I got a Dylos before I learned about AirGradient, and I really like it too. Depending on your budget and tech savviness, it's a great option too.
One important note: these detectors don't do chemistry, and not everything that causes a spike of PM is actually a problem. Showering, for example, will cause a spike for hours, but those salts are probably fine. Running the oven will also cause a spike, and those particles probably aren't fine.
It really depends on where you're coming from.
I have one of those air purifiers from Ikea (Förnuftig). It's cheap but not the cheapest. On any high dust/polen concentration level day, a minute or so with the device turned on at full blast is enough to make any problem go away in that particular room.
Non-anecdotally, I've heard it claimed that indoor air pollution is the #1 factor in reducing the lifespans of otherwise healthy people. No idea if this is the case or what the evidence is, but I don't find it hard to believe.
There is a noticeable improvement but it has not solved the problem by any stretch: so while I don’t regret the purchase, and will keep using it, I am not how sure I’d recommend them for the someone without breathing difficulties / allergies etc.
-Edit- Since so many people are raving about them and recommending you buying an air purifier I want to add this: If you live in a place where the air is truly that bad, my main recommendation would be to move. I have personal experience with this, it's not worth it living like that. You may filter the air in your home but then whenever you go outside you're at risk, if you do sports even more so. Some people wear surgical or cheap cloth masks but these don't actually work.
Don't listen to people who tell you that you can "see" pollution of "feel" the difference. I've lived in some of the most polluted cities in the world and the truth is in most cases for regular healthy people they don't notice anything for years, even at pollution levels far beyond the imagination of folks in Western countries. Most of this is their imagination or placebo like you suspect. For example I've had people complain to me that the air is "so bad" in a place that's naturally foggy and where visibility is often low, but had good air quality. Others were happy about the lovely "clean" skys in a city that gets lots of sunshine but was actually horribly polluted. Also sure, smoke from wildfires is visible (and short lived) but a lot of the pollution from industrial sources isn't. It's a slow and stealthy killer.
1. what that particular filter filters out: ppm, mold, chemicals 2. What is in the air being filtered 3. How sensitive you are to the things in your air 4. How often the rooms air gets filtered through the filter 5. How effective the filter is
I worked in Beijing for a while and going somewhere with filtered air literally felt like a weight was removed some days.
Truly remarkable how well they work, but whether you need one or not depends on whether you have allergens/pollution as an issue in your home. You can purchase an air quality monitor (I have a Temtop M10) or check online measurements of AQI, pollen, etc. for your area. If you have an issue, they work, but not everyone has an issue.
I'll say I'm pretty distrustful of anything but filters personally. My mom purchased a purifier at one point which claimed to use UV light to purify but had no fan to actually pull air through the light, so obviously, it wasn't doing anything.
You're paying for convenience and some bells and whistles (like a mobile app and an air quality reader), but the underlying technology behind it is pretty bare-bones, heavily tested, and heavily used in industrial applications.
It will be a placebo if your home cannot be isolated from outside air or if you don't make an effort to keep windows closed when air is bad.
Also, many expensive purifiers are overpriced junk compared to even simple DIY solutions like those found on particlecounting Tumblr and similar. Ideally the first thing to do is get some reputable air quality monitors.
I've since ended up with a variety of air cleaners:
* IKEA FÖRNUFTIG[0] is a small and relatively quiet unit. It can be wall-mounted, so it can take up virtually no space. The unit is reasonably priced. Filters are cheap.
* IKEA STARKVIND[1] is a much larger unit (also available in end table form[2] to save space), but also relatively quiet on the lower speeds. It's an interesting unit - integrates into Home Assistant (the unit speaks Zigbee), and has a PM2.5 air quality sensor. This unit is a lot more expensive than the FÖRNUFTIG, but the filters are reasonably priced.
* The box fan plus single furnace filter is incredibly noisy, but really good at dealing with cat litter dust. There is a huge range of price/quality when it comes to filters[, I just use the cheaper ones since I'm focusing on large dust particles.
* I have a couple of units that use Bionaire aer1 filters[3]. The units I have are quiet and reasonably sized, though they get louder as the filter fills up. The filters are expensive, and one of the units takes two of them which doesn't help matters. There is a variety of filters available.
There's a huge spectrum of tradeoffs between noise, size of the unit, filtration effectiveness, replacement filter cost, and extra features. I'm not convinced I've found the sweet spot yet.
[0] https://www.ikea.com/ca/en/p/foernuftig-air-purifier-white-5...
[1] https://www.ikea.com/ca/en/p/starkvind-air-purifier-black-40...
[2] https://www.ikea.com/ca/en/p/starkvind-table-with-air-purifi...
[3] https://www.bionairecanada.com/en_CA/service-and-support/aer...
And yes it definitely makes a difference. Sometimes when I open my windows to get some “fresh” air and remove the co2 from my room, the ppm momentarily goes up. Also very useful for cooking since I don’t have a great vent. Ocassionaly when frying something ppm goes over 200 but it quickly drops down with the air filter.