Are there good indoor air quality monitors?

May 16, 2023 8:23 AM

Wirecutter ended up concluding that all indoor air quality monitors were unreliable. I know this is a long shot, but has this changed in the eight months since?
posted by ignignokt to Technology (10 answers total)

I don't know from air quality monitors, but I wouldn't necessarily trust Wirecutter's opinions on the matter.
posted by alex1965 at 8:47 AM on May 16, 2023 [7 favorites]

From the folks who brought you the really great $250 CO2 sensor, there is an Aranet particulate sensor. It is $250 and has to be plugged in, and but if they say it is accurate, it is accurate. I'm sure it's not accurate to a micron like the regulatory compliance sensors, but Aranet's specs on the CO2 monitor have been confirmed multiple times, they are a reputable manufacturer of (comparatively) affordable instruments. The other downside of this Aranet one is that you'll only have a green/yellow/red LED output, it doesn't have a display. To get numbers out of it you'll need a base station which is another $250 ish. But I would take one that is going to work over something unreliable blithely sporting three digits of accuracy when it don't even have one.
posted by wnissen at 9:38 AM on May 16, 2023

They didn't test literally the only one I've ever heard of, which is the PurpleAir monitor, but did say "PurpleAir sensors proved quite accurate when California’s South Coast Air Quality Management District tested them against professional equipment (PDF)." So.... I'd check out PurpleAir?
posted by brainmouse at 10:55 AM on May 16, 2023

Air quality is a complex thing that can't be measured in one dimension; I can imagine a 'food quantity measure' that is a cup on a cheap spring scale that does a reasonable job at measuring liquid volumes of around a cup, an okay job at measuring the weight of the food, but a poor job of measuring half a teaspoon of something. The Wirecutter article doesn't say that they are all unreliable, it says that they have a problem in the measurement of a specific thing -- VOCs (chemicals found in things like alcohols, cleaners and paints), where the sensors wear out in a short period of time -- and I suspect this hasn't improved in eight months. There are still quite good consumer AQMs for measuring other aspects, like CO2 (literally caused indoors by exhalation, and a proxy for COVID and other respiratory diseases in crowded areas) and PM2.5 (the fine particles in exhaust, dust and smoke that can get into your lungs).

This link goes to the South Coast AQMD (the Los Angeles area agency monitoring air pollution) tests of a wide variety of air quality monitors including many of consumer grade. This is specifically for PM2.5 (and other similar particle sizes) monitors. The field and lab R2 columns show how well the monitor matches the professional gear that they use. The higher the R2 the better; many devices have lab R2 of 0.99 or so. (The other columns show MAE; the lower the better for this one).

I have a Temtop model, which is both the Wirecutter pick for PM2.5 and which performed well in the South Coast AQMD tests (and is the cheapest model on the table). Today, my city was engulfed in wildfire smoke, and it was very helpful in figuring out where in the apartment the smoke was coming in, and in measuring how well the air purifier is doing at cleaning it up. It's also good for cooking smoke and oil vapours (it detects them before I notice) and helping get those vented quickly. The CO2 monitor seems to work well, although that's not something that matters for me (there's only me and my wife in my apartment).
posted by Superilla at 11:21 AM on May 16, 2023 [2 favorites]

If what you are looking to measure is C02 levels, either for their own sake or to use C02 levels as a proxy for COVID risk,

I've seen medical experts/virology experts recommending

Aranet4 HOME CO₂ sensor

This is the link to the Australian site, with prices in Australian dollars - the price in the US will be much lower because of currency conversion rates.
posted by chariot pulled by cassowaries at 11:22 AM on May 16, 2023

I've been tempted by the uHoo home monitor but haven't pulled the trigger yet. I heard of it via someone on Twitter back when the gas stove emissions issue was first reported a few months ago, as it's one of the few monitors that includes a sensor for NO2. What reviews I've seen seem solid.
posted by sapere aude at 11:25 AM on May 16, 2023

The AirGradient kits are pretty well regarded, for their comparatively low cost: https://www.airgradient.com/open-airgradient/kits/

I plan to build one this summer.
posted by wenestvedt at 7:32 PM on May 16, 2023

They didn't test literally the only one I've ever heard of, which is the PurpleAir monitor, but did say "PurpleAir sensors proved quite accurate when California’s South Coast Air Quality Management District tested them against professional equipment (PDF)." So.... I'd check out PurpleAir?

I have a PurpleAir sensor indoors and outdoors. I find its measurements to be accurate insofar as both the indoors and outdoors monitor readings line up well with an independent third-party handheld air quality monitor.

If PurpleAir is inaccurate, then other monitors are inaccurate, and vice versa. There would be some kind of conspiracy to make all such monitors inaccurate, which I do not believe for the simple reason that that would be a huge multi-nation, multi-corporate conspiracy to undertake. That's not impossible, but very hard for me to believe without a lot more evidence.

Whatever else, PurpleAir also lets you publish your sensors' readings online for all to see, and those outdoor measurements are also consistent geographically with other outdoor sensors in the region, which are not made by PurpleAir.

I would put huge doubt on Wirecutter's findings, in this instance.
posted by They sucked his brains out! at 10:49 PM on May 16, 2023

Measuring stuff is often much more complicated than it seems: Why PurpleAir and AirNow show different AQI scores during wildfires

A lot of CO2 sensors assume that they will be exposed to outside air (~400 ppm) regularly and auto-calibrate based on that assumption. So a sensor left inside 100% of the time (without any open windows) may slowly become inaccurate.

While it's nice to buy an "measure everything" monitor, I'd be wary because each sensor operates differently and may fail separately. Maybe think about what you want to measure and get sensors specifically for that.
posted by meowzilla at 11:19 AM on May 17, 2023 [1 favorite]

It would be good to know what you want to accomplish. When I was searching for this I was wondering about CO2 levels mainly. I bought the Awair Element they mention. I haven't had any of the problems they encountered, but I mainly use it passively: to send alerts if something is out of normal bounds and when I happen to walk by the unit since there's a simple summary on the front. It's worked for us for what I wanted to do and I check in on it once in a while by cooking bacon from a floor away.
posted by yerfatma at 11:53 AM on May 18, 2023