Review: Airly PM + Gas

There is an enormous demand for air quality monitors in cities near forests that are susceptible to wildfires. Climate change has driven huge increases in wildfire area burned over the past few decades, and air quality data can help us protect public health more than ever.

Watch out! Wildfires are not the only source of air pollution in cities. Urban lifestyle with huge diesel/petrol SUVs and delivery trucks moving all around the city all day long emit huge amounts of toxic pollutants (NO2, CO, UFP, etc…) and during winter season wood stoves emit extra 12 times more PM2.5 pollution into the air we all breathe as a result they create an unhealthy environment for all.

Airly is an aspiring company that tries to empower individuals and communities with knowledge about the air they breathe by offering three different monitors that will meet the needs of a different situation. The Airly PM with is the basic version and measures particulate matter PM10, PM2.5, and PM1.0, the Airly PM + Gas (NO2 + O3), and finally, the Airly PM + Gas (SO2 + CO).

For this review, I will present to you the Airly PM + Gas (NO2 + O3) as I believe it represents better the urban environments free from industrial sites. In my city, the number one pollutant is ground level ozone as there is a huge production and transportation of vegetables and fruit all around Spain and Europe and plenty of sunlight.

Keep in mind, ground ozone forms from the interaction of nitrogen dioxide and some other pollutants with UV radiation from the sunlight.

Technical Specifications

  • PM1.0/PM2.5/PM10 sensor
  • Nitrogen dioxide (NO2) sensor
  • Ozone (O3) sensor
  • Temperature
  • Humidity
  • Pressure
  • GSM (Currently available)
  • Optional: WiFi, LoRa (Coming soon)
  • RGB LED Light
  • 3 meter USB-A Cable

Although most companies sell the air quality monitors in a package and most individuals cannot afford the initial cost especially when they feature gas sensors, Airly provides the monitors under a subscription model. They offer the Standard and Enterprise plan which can begin to as little as 15 euros a month plus the fixed cost of the device between 100-300 euros.

The monitor comes with a key that allows you to lock it on the support plate. The support plate comes with a very strong adhesive on the back in order to place it anywhere you like. I was unable to remove it from the tile that I had placed it, so you shouldn’t worry about falling down or getting stolen.


The whole device and the support plate are made with high-quality stainless steel metal, something not commonly found.

It features the Plantower PMS5003, a widely know low-cost sensor for accurate PM2.5 measurements. Many monitors use this sensor for ambient air monitoring, it is considered one of the best with a correlation coefficient R2 ~ 0.87, however, it may overestimate concentrations sometimes.

In general, NO2 sensors are very unreliable because of the nature of the gas. Nitrogen dioxide transforms into the air to form gaseous nitric acid, toxic organic nitrates, and ozone, for this reason, it is difficult to measure it. The performance can be increased significantly when adding additional measurements of temperature and humidity in a regression model or neural network. The presence of the Ozone sensor can give us even better NO2 results. However, I need to co-locate the monitor inside a reference AQ station in order to determine the accuracy of the gas sensors.

The temperature, humidity and air pressure sensor seem to comply with the reference station measurements even though the station is 1km away.

Airly uses algorithm to improve the quality of both the PM & Gas sensors.

App/Web Panel/Open Map

The app is called Airly, and it is available for iOS and Android devices. Apart from the proprietary monitors it also supports official AQ state stations like the US EPA and 3rd party monitors, which enrich the experience of the users by creating denser maps with more AQ information.

The app supports notifications and also includes 24h forecasting with 1h resolution time thanks to predictive algorithms.

It supports the European CAQI and the US AQI algorithms to assist both European and North American users and of course metric, and imperial metric systems for temperature, humidity and pressure values.

Airly iOS app

The Web Panel is available for those subscribed to the Enterprise plan provides predefined reports and access to raw data (real-time and historical).

Airly Web Panel

The open map is available for all, you don’t need to have an account or a monitor to benefit from it. It is very well designed and offers a lot of information. It supports Dark Mode theme for those who want to check the air quality late at night or hate bright displays like myself.

Airly Open Map

My Experience

Easy setup, basically, it is a plug and play solution, just think wise about the place you are going to install the support mount/plate of the monitor.

The app and open map are super snappy, you don’t need to wait to get access to the live measurements, which I really value.

Regarding the NO2 and O3 gas sensors, I was able to measure events of high NO2 during peak hours in the morning and afternoon. In the morning, when people go to work, I always get a spike of ~55µg/m³, which has created a pattern hard not to acknowledge. The ozone sensor registers high concentrations of the gas at 15:00 with values reaching 91µg/m³ when sunlight UV radiation is at peak.

I miss the presence of a settings page to manage some features of the monitor like turning on/off the LED and being able to adjust the frequency the device takes a measurement. The default value is set to intervals of 5 minutes but the company told me that they can change it under a specific request. The LED provides great feedback (Green=Good AQI, Yellow=Moderate AQI, and Red=Unhealthy AQI), but when you place a device in a public area you have to be careful not to draw attention and avoid vandalism.


I find Airly PM + Gas very compelling for communities and schools that want to measure the outdoor air quality, the app and the open map are well designed and easy to interact with. An in-depth analysis of the sensors is needed in order to determine the accuracy and frankly further calibrate them.

Some users argue that a subscription model is not sustainable. However, this is not the case, as it guarantees that clients will constantly receive support, and all expenses are covered like configuration, calibration, GSM data, and replacement of a unit in case it breaks.


8 thoughts on “Review: Airly PM + Gas

  1. I really don’t understand why AQMs like this bother with average to poor PM Sensors like the Plantower or Sensirion. They give average results at PM2.5 (+/-10-20% as compared to an expensive reference instrument) but interpolate PM1 and PM10. Those figures can be as much as 75-80% off. Better to look at for an accurate low-cost PM Sensor.

    Liked by 2 people

    • Interesting information about the Piera Sensors. Are there more studies about long term comparisons to different reference instruments and examples of large scale applications of this sensor?


  2. Nice write up!
    Seems that there might be a market for leasing/renting AQM. Some governments need them for 6-18 months and then – no more.

    That’s a nice enclosure (especially when compared to PA, which uses a 3” PVC pipe cap! ) with the stainless roof. Looks like a real product.

    I also think there might be a market for calibration. Send devices to a company that validates / certifies.

    I remember the SDS011 has a useful life of about 3 years. So few people will replace it when it is past it’s life. Would be good for to have an elapsed time counter.

    Keep up the good work. I’m lurking a bit on and getting to know that organization better.

    From: See The Air
    Reply-To: See The Air
    Date: Monday, October 26, 2020 at 1:19 AM
    To: Dave Clark
    Subject: [New post] Review: Airly PM + Gas

    Sotirios Papathanasiou posted: ” There is an enormous demand for air quality monitors in cities near forests that are susceptible to wildfires. Climate change has driven huge increases in wildfire area burned over the past few decades, and air quality data can help us protect public hea”

    Liked by 1 person

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