Review: AirAssure an Indoor AQ Monitor by TSI

Someone may ask what more they can offer to an already saturated market of air quality monitors. The answer is simple: Experience! TSI Incorporated is a USA-based company with more than 60 years of experience and knowledge thanks to the 1000 researchers and engineers that work for the company worldwide. They hold more than 50 patents.

Recently, TSI released the AirAssure which is an IoT-enabled Indoor Air Quality Monitor (AQM) designed specifically for buildings that really need to have an in-depth and accurate view of the indoor air quality. The monitor comes in two versions the 4-gas and 6-gas variation. I am going to review the 4-gas AirAssure IAQM that comes with a Formaldehyde, Carbon Monoxide, Carbon Dioxide, and Total Volatile Organic Compounds sensors. Apart from the 4 or 6 gas sensors configurations, all versions come with a particulate matter sensor and a temperature/humidity/barometric pressure sensor. Also, a new CO2 and VOC model will be released this autumn.

Technical Specs 4-Gas AirAssure

  • Formaldehyde (CH₂O)
  • Carbon Monoxide (CO)
  • Carbon Dioxide (CO2)
  • Total Volatile Organic Compounds (tVOC)
  • Particulate matter (PM)
  • Temperature, Relative humidity and Barometric pressure
  • Universal USB-A Power Adapter
  • USB-A to USB-C Cable
  • USB-C port
  • Included 32GB Removable micro-SD
  • 24 VAC Terminal Connector
  • Colour LED Lights

The AQM isn’t very compact but this is a good thing because the sensors have space between each other and there is no unwanted heat interference. The dimensions of the monitor are 13.3 cm long, 4.8 cm tall, and 3.5 cm deep that offer plenty of space for the correct operation of the monitor. In comparison, other AQMs suffer from heat dissipation as electronic components are crowded and get hot. Another common issue with design choices is bad coupling to the ambient environment as it can result in significantly decreased performance and increased response time, TSI has taken all of these parameters into consideration with their design to provide more accurate readings.

It comes with a color LED array of 4 lights that will help you during the initial setup. The monitor uses state-of-the-art, low-cost sensors to deliver accurate data back to the users. It is the first monitor (in my relocation) that uses a Dual-Channel NDIR CO2 sensor for superior stability.

Dual-Channel NDIR CO2 sensors (aka Dual-Beam) contain two IR detectors, one tuned to CO2 gas absorption and the other at reference, unaffected by CO2 gas concentration. As the sensor drifts over time, the reference channel will experience a change in output due solely to these effects, which can be applied as an offset to the active measurement channel as compensation. In contrast, single channel NDIR sensors use a statistical algorithm called Automatic Background Calibration (ABC) to determine and apply drift compensation.

The presence of the Formaldehyde sensor offers an extra layer of information that will help us identify the source of pollution indoors. VOC sensors alone sometimes create confusion to the users because of the great number of chemicals they can detect. Ethanol aka the alcohol inside the disinfectant gels and wipes interference with VOC sensors but the Formaldehyde sensor has a low cross-sensitivity to it so we can get a more accurate picture of the indoor air thanks to it.

Carbon Monoxide sensors are designed to save lives as even small concentrations of this gas are lethal. Concentrations above 150 to 200 ppm can cause disorientation, unconsciousness, and death in hours. Indoors, 9 ppm is the maximum safe carbon monoxide level over 8 hours.

The micro-SD card is there for the experts who cannot connect to Wi-Fi and want the data no matter where the device is placed (remote location, or in the basement). Some people don’t have internet access yet. The data are always available to the user.

The particulate matter, tVOC, temperature, relative humidity, and barometric pressure sensors are the best low-cost ones you can get in the market right now.

Dashboard (TSI LINK)

Solid solution and easy to use. At first, you have to personalize the main dashboard with your widgets that can be added with a click of a button. In my case, I have one with the current readings, which has a very unique feature. It tells you about the average AQI values from PM2.5 measurements for 30-minutes/1-hour/6-hours/24-hours/1-week. Then you can add a lot of widgets, like histograms and maps from difference devices that are in different locations.


Users can manage their devices easily and see their status on the Devices management tab. There, you can set new alerts, adjust the logging interval, set a cleaning interval (Daily or Weekly), calibrate the values of the sensors, make the data public (like I did), and many more. You can also share the data with others by inviting them to the dashboard.


Your devices appear on the map but other indoor and outdoor monitors will appear too as long as they are set as public by their owners. You can click on them and see the histograms and current and average values.


My Experience

I know that many of you are waiting for my personal experience as you value my honest opinion.

I really like the internal design choices of the company, I can see their distilled knowledge take form in the device in order to offer a great product. Lots of scientists are asking me for AQMs with an internal memory where they can store all the measurements without the need for a subscription or internet connection and the AirAssure can offer just that in a 32GB micro-SD memory.

Something that I dislike is the finish of the outer plastic as it doesn’t feel very polished. On the other hand, experts can easily take the device apart and replace or clean the sensors. Also, on the dashboard, I would like to have the option to change between metric and imperial values across all measurements easily. In my case, I understand Barometric Pressure in hectopascal (hPa) values but I have to use Inch of Mercury (inHg) at the moment as there isn’t any other option. I am sure in the future they will address this small issue. The LED array also needs to reflect the general IAQ score or a specific IEQ parameter, like CO2 or PM2.5.


All in all, TSI has developed an indoor air quality monitor equipped with all the necessary sensors for two different scenarios. The AirAssure with 4-gas sensors makes sense for white-collar employees, students, and general residents. In contrast, the AirAssure with 6-gas sensors is more suitable for blue-collar indoor employees. However, if ports or busy roads, or refineries are near your building then the 6-gas version makes more sense for you.

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