By: Gustavo Olivares
Because of its significant cost, monitoring air quality used to only be available to government agencies. However, over the past decade, cheaper air quality sensors have made it to the market and have been used in earnest by many people, from researchers to businesses, communities, and individuals. Our team has been working with these low-cost sensors since they appeared back in 2012, and here we present the devices we currently use the most, and our reasons for choosing them.
Please keep in mind that this is not an endorsement of any of these devices but a documentation of our thinking when selecting air quality monitors. Also, we have not received any incentive by any manufacturer. These are just the ones we use, there are a lot of other sensors on the market that we haven’t yet tried, so can’t comment on.
A note on ODIN
Some might know of our very own ODIN (Outdoor Dust Information Node) and might wonder if we’re still using and making them. Well, we still have quite a few of them in storage but their enclosures are starting to break and their batteries are several years old now so they’re failing more tfrequently. As a result, we only have them now for our internal research and development activities and to test some ideas.
Outdoor measurements
At the moment, our main outdoor monitoring devices are Clarity’s Node-S and Air Gradient’s Open Air and Open Air Max.
Clarity Node-S
This is a compact, 4G connected solar-powered air quality sensor designed for outdoor deployments. It’s part of Clarity’s broader environmental monitoring platform and is often used by cities, researchers, and community groups. The version we use most measures PM10, PM2.5, Temperature and humidity.
We have been deploying many of these sensors since 2022 in places like Invercargill, Hawke’s Bay or Alexandra, and they have proven extremely reliable in terms of data capture and ease of deployment.
They do have, however, a couple of downsides. Their annual subscription model makes them a bit more expensive for multi-year, or for short-term deployments but it’s difficult to argue with the reliability of these units. Also, their system is closed source so there is no documentation about the firmware and changing the operation is not possible. Finally, the Node-S doesn’t have any internal data storage capabilities so if the instrument doesn’t have a mobile phone signal to send data, those data will be lost.
Air Gradient Open Air 
This is an open-source, DIY-friendly, WiFi connected, air quality monitor designed for indoor and outdoor use. It’s part of AirGradient’s mission to make air quality monitoring more accessible and transparent, especially for schools, communities, and researchers. We have only recently started to work with these but are so far very impressed with the openness of the system and the data platform. The version we’ve used is the O1-PST that measures a range of pollutants like CO2, PM10, PM2.5.
Being DIY-friendly, they have a “kit” version to put together by yourself and they have very well documented hardware, software and firmware. They integrate out of the box with Home Assistant, which makes them work very well with our Smart Home Air Quality System (SHAQS).
The main downsides of the Open Air for our purposes are the lack of a solar panel and the fact that it requires WiFi to operate. They work well for our “residential” projects but they are not an option for neighbourhood-wide deployments because of the general lack of town-wide WiFi networks. Similarly to the Clarity Node-S, it doesn’t have on-board storage so data not transmitted is lost.
Air Gradient Open Air Max 
This is the more advanced version of the Open Air monitor, designed for advanced users and those who want to deploy sensors outside WiFi coverage and with limited power availability. It builds on the open-source foundation of the original Open Air but includes a solar panel and a more robust enclosure suitable for outdoor use. Again, we’ve only started using these recently, so cannot fully vouch for their performance yet but their specification and our early experience is promising.
Similarly to the other outdoor devices, the “Max” doesn’t have on-board storage available and therefore any data not sent via the 4G modem, is lost. However, given the openness of the firmware, it is possible, in theory, to add on-board storage capabilities for specific projects. Another issue that we’ve found is that the power management of the Max is not as aggressive as that of the Node-S that changes its data communication frequency when the battery level is too low. This can potentially impact the deployment of the Max in low sunlight environments like deep street canyons or high latitudes.
Indoor measurements
Qingping Air Monitor Lite 
For indoor measurements, we have almost exclusively used the Qingping Air Monitor Lite since 2022. This little device has performed extremely well for us. Its PM sensor is the same that powers the outdoor devices discussed above, and the photo-acoustic CO2 sensor performs just as well as the NDIR sensor that’s present in the Aranet4.
The Qingping BlueTooth broadcast is integrated seamlessly with Home Assistant and, by having a WiFi connection available, there are two ways of capturing the data, as we do in our SHAQS (Home Assistant for BT, and Qingping IoT platform for WiFi).
The only issue that we’ve occasionally encountered with these devices is that they can stop connecting to the BT hub or WiFi network and the only way to recover them is to completely re-configure them. It hasn’t happened very often, but when it does, it means lost data.
Aranet4
The Aranet4 is a compact, battery-powered CO₂ monitor that we’ve used in many of our indoor deployments. Its main advantage is its very low power consumption with its batteries lasting a few years, making it ideal for long-term monitoring in places without easy access to power.
The device is simple to use and provides reliable CO₂ readings, but it does come with some limitations. It only measures CO₂, temperature and relative humidity so it’s not suitable for projects that require particulate matter. Also, only the Pro version supports telemetry that doesn’t rely on a smartphone which pushes the price up slightly.
Despite these constraints, the Aranet4 has proven useful in specific scenarios where power efficiency and portability are more important than multi-parameter sensing.
Conclusion
Deploying a mix of low-cost air quality sensors has taught us a lot—not just about the technology itself, but also about the practical realities of monitoring air quality in diverse environments.
Choosing the right air quality sensors is about more than just specs and price—it’s about finding tools that align with your goals, values, and practical constraints. For us, that meant selecting a mix of devices that offer reliability, openness, and affordability.
From the solar-powered Clarity Node-S to the customizable AirGradient Open Air and Open Air Max, and the user-friendly Qingping Air Monitor Lite, each sensor plays a unique role in our monitoring strategy. Together, they help us build a clearer picture of the environments we care about—whether indoors, outdoors, or somewhere in between.
We hope this breakdown helps others navigating similar decisions. If you’re exploring low-cost air quality monitoring solutions, we’d love to hear what you’re using and what you’ve learned. Feel free to reach out and share your experiences, we will share our own in return.
