The Problem

Clean air is becoming a scarce for many reasons beyond the scope of this article, so it’s not surprising that the air purifier sales are on the rise. Although home ventilation and air purification are necessary, it can be easily overdone, which leads to higher electric bills and causes noise pollution (air treatment is a noisy process). The only way to know if your air is good enough is to have an air quality monitor, and there are plenty of good options on the market, although most of them have some serious downsides.

How to Choose an Air Quality Monitor

Unfortunately, unchecked profit seeking can lead to some perverse incentives, and smart home device market is one of the shadiest ones. Most air quality monitors above $200 are accurate enough to tell you if you have a problem with your indoor air quality, but they can’t control your air treatment systems, so they aren’t able to fix any issues they detect.

Most private companies hate open protocols and interoperability, because giving users more freedom and flexibility can hurt their profits, but there are a few companies, such as AirGradient, which tend to restore my faith in humanity.

AirGradient products seemed good and affordable enough (~$100 for a high accuracy monitor), so I decided to try their so-called Pro Kit, which is basically a reasonable accurate air quality monitor with an open source firmware and hardware.

Delivery

The delivery took seven days, and it wasn’t easy to figure out how to track it. That’s one of the things which can be improved and I let the company know about that issue. It’s a pretty small company, so I expected some minor issues and inconveniences, because it’s a small price to pay for a product with this level of transparency and repairability.

As you can see, the box itself was manually prepared by someone, which gives the product an uncommon, hand-made feeling:

The box itself had minor bumps here and there, but there was no damage to its contents:

Onboarding

I expected to find an assembly instructions in the package, but I found a QR code instead. Scanning that code redirects you to AirGradient website, where you can find the assembly instructions. Websites are more ephemeral than the physical boxes, so I don’t really like the idea of introducing such a dependency, but it makes total sense if you want to cut costs and be able to edit the assembly instructions after shipping the product.

Anyway, I hope there will be a way of getting a printed manual in the future.

Assembly

I ordered a pre-soldered kit, so the only thing I needed to do is to connect a few components to the mainboard and close the case. Some components, such as display and PM 2.5 sensor, were already connected, so I only had to connect a microcontroller, a CO2 sensor, and the unified temperature and humidity sensor:

Accuracy

AirGradient Pro only uses well-known and affordable sensors, which are accurate and reliable enough to be used to monitor air quality at home. Those sensors are far more accurate than the stuff you would find in an average sub $100 air quality monitor. Here is a picture of one of the most popular budget air quality monitors standing nearby AirGradient Pro:

I just stepped into a well-ventilated room before taking that photo, and the other sensor immediately jumped from ~400 to ~1,300 CO2 ppm, which is simply impossible. AirGradient numbers felt a bit off, too, since I expected ~450 ppm, but it’s known to show somewhat less accurate readings till it self-calibrates, which is happening automatically once a week. I checked the readings after the first self-calibration, and they were within the advertised +- 70 ppm precision.

Conclusion

I’m happy with my AirGradient Pro, and I’ll probably order more monitors, because I want to monitor every room as well as the air quality outside my house. I enjoyed assembling this kit, and it also reinvigorated my interest in microcontrollers. It reminded me that I have an old Arduino kit, which I bought ten years ago, and I was finally motivated enough to check it out and finish all the projects described in its official guide.