Tracking air quality

I’ve had a Netatmo indoor weather station in the bedroom for the past few years, which has given me a rough idea how fast CO2 builds up when the windows are kept closed, and how fast the levels drop back down when the windows are left open, under different conditions.

I also have a small air purifier, and would like to get an idea how long it should be run at what intensity, and when it’s even worth using (if at all). Unfortunately, the Netatmo does not measure particulates in the air.

Somewhat related, I’d like to know how effective the car’s cabin air filter is over its lifetime, and under what situations it’s better to recirculate air (trading off particulates for stale air).

So I’m looking for a device that can measure both how stale the air is (CO2 or VOC) and what the concentration of particulates in the air is (PM2.5, maybe PM1.0 and PM10), and that is portable enough to be carried along into the car. Some devices I’ve come across:

  1. IQAir AirVisual Pro measures PM2.5 and CO2, exports data, is somewhat portable, and has been shipping for a while now.
  2. Plume 2 measures PM1, PM2.5, PM10, NO2, and VOC, exports data, is very portable, and just started shipping recently.
  3. Wynd Halo measures PM1, PM2.5, PM10, CO2, and VOC, is somewhat portable, and claims to be shipping (though some customers claim otherwise, and I’ve seen no proper reviews yet). Also, not sure about data export (waiting to hear back from them).

Does anyone here have experience with any of these devices? Or are there other devices I should be considering?


Heard back from Wynd: no data export, at the moment.

I’ve seen some presentations using DIY particulate sensors, like this one: Is that too much hassle?

Could be a fun project, but the soldering iron can’t be good for the air quality :slight_smile:

I spoke at the QS conference a few years back (maybe there’s video?) about an air quality sensor I built via - that project is dead but you can just copy the plans and order the sensors/arduino.


Also, I have recently been using the Flow device by Plume Labs as a personal air quality device - it can be attached to your bag/backpack, clothing, etc. and their app can combine air quality data with location so you can do interesting things like map the air quality around town (great for avoiding high pollution areas while running/biking, etc.)

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Thanks, just placed an order for the Flow 2.

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This is awesome but I hate to say I don’t want to think about charging it alone with all of my other electronics. Anyone tried getting a portable battery for it so it can run for a week or two?

Unless you are traveling for several days, simply keeping the Flow 2 on the base station it ships with whenever you are at home seems like less trouble, no fiddling with charging cables and batteries.

Some initial impressions of the Flow 2:

  • Setup was about as quick and painless as can be expected…
  • …until the app stopped receiving data. Resolved with a factory reset; hope this was a one-off.
  • Bluetooth is a bit flaky (a common problem with Android apps). In consequence, the location data has gaps, but I can do without that.
  • They want you to take the device with you everywhere, but you’re not supposed to expose the device to any humidity or too much sun or dust???
  • The in-app data display is a bit lacking… Fortunately the data export via emailed link includes all the data (minus time zone offsets, which they may not capture, and timestamps of spot measurements, which would have been a convenient way to mark events like opening or closing a window).
  • Of the data I’ve seen so far, some data points look plausible, other data points less so… Too soon to judge, as you’re supposed to give the device a week to calibrate itself (how this works they won’t say, apart from some hand-waving about AI).

visit your local maker or hacker space

This could mean the sensor itself is poor or jittery.

The NO2 data does seem a bit jittery:

…but yesterday was worse :slight_smile:

Cheap sensors have drift and other issues; we’ll see how well the software is able to compensate for that.

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what does the VOC graph look like?

Calibration usually requires testing a very well known quantity and should have been done at the manufacturer.

Plausible, i.e. stable or rising when indoors, and dropping when windows are opened or I go outside. Going to check how closely Flow’s VOC tracks Netatmo’s CO2.

Even if a sensor ships calibrated, it will drift and need to be recalibrated periodically. Netatmo for example does this by assuming that CO2 drops to background levels at least once a week. Fine with me, but important to know!


  • NO2 has stabilized. There are still occasional spikes, but they are removed retroactively.
  • Location data is captured more or less reliably, but only while the phone screen is on.
  • Took the device along for a hike in a coastal area yesterday. Air quality showed as excellent, except for very high PM10 (AQI up to 100). This might have been due to sea salt aerosols (it was quite windy).
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Wynd looks awesome. That’s a shame there’s no data export.

Brief update:

  • Recirculating air for an hour or more while driving doesn’t appear to increase VOC much (at least not with just two people in the car), and filtered outside air doesn’t increase PM values, even in dense traffic. Next I could try driving around with open windows, and if that doesn’t do it, maybe drive through some tunnels? :grin:

  • PM1 has always been close to zero, except for one spike in a “food hall” with open kitchens.

  • Running the dishwasher at home results in a brief but large increase in PM10, unless I keep a window open, which I’ll probably do from now on.

  • Running an air filter at home seems pointless right now, as doing so doesn’t change any of the already low values. Will reconsider once outside air quality gets worse.

  • NO2 values still go crazy regularly, especially when the sensor is left stationary.

  • Reading this article about air pollution in our homes, I learned about the HOMEChem project. Could be a useful resource to look for explanations for mystery indoor pollution spikes (like the dishwasher)!


Great write up! Im looking to get into air quality. Do you think the flow 2 or the Netatmo indoor weather station would be good to have running 24/7 in my bedroom?

The Netatmo also records room temperature and background noise levels, which can be valuable when looking at factors that affect your sleep. Plus once it’s set up, it doesn’t require any care and feeding. But it won’t tell you much about air quality, other than CO2 build-up.

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Thanks Eric! Think I might grab one. I do have a hepa filter in my studio so not worried about air quality really but would be nice to see if some pollutants are still lingering.