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Hi everyone,

It's been a while since issue 04, and I'm sorry about that. I ran into some problems with my air purifier testing methodology, and fixing them has eaten up hours and hours every day for the past few weeks, spent (re)testing the devices. But in that time, I also got the chance to publish one of my most requested reviews.

Back in issue 02, I mentioned I'd been chasing an IKEA Alpstuga for months, and that stock problems across four countries were making the whole thing quite a painful experience. I finally landed three units in Los Angeles, and after two months of testing, wrestling with a Thread network, and staring at graphs longer than I'd like to admit, the full review is live. If you want to learn all the details, please refer to the full review. However, I also wanted to highlight some interesting aspects here because at $34.99, this device is genuinely unique in a good way.

Nothing else on the market gives you PM2.5 and CO2 sensing (at least at any decent level of accuracy), a screen, and Matter connectivity for anywhere near this price. A standalone CO2 sensor module alone can cost close to what IKEA charges for the whole assembled device. But, is there a reason for that?

I ran all three Alpstugas next to two AirGradient monitors for two months, and the shape of the data agreed well across all five sensors. When cooking smoke spiked the room, every device climbed and settled together at the same moments. What surprised me was how far apart three identical units could land on the actual figure.

During one morning peak, the three Alpstugas read anywhere from 280 to 440 µg/m³, a spread of over 150 µg/m³ sitting side by side on the same shelf. Sensirion rates these modules at roughly ±5 µg/m³ below 100 µg/m³ and ±10% above that, so a 40% gap between units is well outside spec.

My best guess is that it comes down to how the sensor gets calibrated against a KCl solution at the factory, which looks nothing like real cooking smoke to an optical sensor. The trends are shown, but be careful with the individual numbers.

This is where things got interesting, and also where I nearly gave up more than once. The Alpstuga uses a thermal-conductivity CO2 sensor instead of the NDIR sensors you'll find in most decent monitors, meaning it reads CO2 indirectly by measuring how the air conducts heat. IKEA and Sensirion both say to give it twelve hours to settle before interpreting the readings.

Across three units and three separate test runs (that lasted multiple weeks each), I found that it took me closer to a week before the readings lined up with my NDIR baseline. Even after that, accuracy tracked room temperature closely. Right around 25°C, the Alpstuga matched my NDIR sensors almost exactly. Push the room warmer or cooler and the gap opened back up, sometimes by a few hundred ppm. The sensor is rated at about ±100 ppm to start with, so this isn't a device for anyone who needs a precise number. However, it can act as a general indicator.

The Alpstuga runs on Matter over Thread instead of Wi-Fi, so you'll need a Thread border router somewhere in the house before any smart features work. Thankfully, these are more common than people assume (an Apple TV or any modern Alexa device will do), but if you have nothing, you're stuck with just the on-device screen. IKEA's own DIRIGERA hub can act as a border router too, though at $109 it's a pricey way in when cheaper and more useful options exist.

Pairing itself nearly made me give up before I even started. I spent a good half hour resetting units next to my Apple TV before they'd connect, and at one point I had a browser tab open to buy a Thread antenna, convinced my network was the problem. It wasn't. Once paired, though, the Alpstugas have been flawless, surviving a power cut and rejoining the network on their own while half my other smart devices needed manual help.

That leads us to the question: is this the best $30 sensor out there? For blanketing a home in air quality data, probably yes. Nothing else (that I know about!) touches PM2.5, CO2, temperature, and humidity together at this price, and the connectivity has held up better than gear costing twice or three times as much. Just don't buy it expecting NDIR-grade CO2 numbers, because you won’t get those. My full review has all the graphs, the three separate CO2 tests I ran to make sure I wasn't imagining things, and a breakdown of how it stacks up against the Vindstyrka, the SwitchBot Meter Pro, and the Qingping Air Monitor Lite.

As always, thanks for reading and for being part of the community!

Ethan