Air pollution expert Sotirious Papathanasiou has been testing out the Analox Air Quality Guardian and gives his in-depth review below:

This is the second Analox product review that I have written on my blog. I like the product range and the solutions that Analox offer to professionals. The first review was about the CO2BUDDY, a portable/wearable carbon dioxide (CO2) monitor. In this review, I will write about the Air Quality Guardian. The Air Quality Guardian is a CO2 monitor station, designed for those that don’t want unnecessary smart features and too many bells and whistles.

The large LCD display provides plenty of clear information for those professionals that don’t have the luxury of time to continually take their phones out of their pockets in order to check the CO2 concentrations and trends. Keep in mind, the monitor measures other environmental parameters as well.


  • 4” backlit LCD screen
  • CO2 Sensor Low drift NDIR (Non dispersive infra-red) CO2  sensor with a long lifespan
  • Temperature and Relative Humidity Sensor
  • Simple 4 button navigation
  • Built-in data logging
  • Simple three-level indoor air quality indication system including:
  • Configurable audible and visual alarms
  • Power and charge via mini USB
  • 8 hour battery backup
  • Wall mountable or desktop
  • Dimensions 120 x 90 x 35 mm 4.75 x 3.5 x 1.4 in
  • CE, UKCA, RoHS 2.0 and FCC compliant
  • CO2 Sensor specs
  • Measuring range 0-5000ppm
  • Accuracy (0~3000)ppm: ± 50ppm ± 5% of reading (take the Maximum) (>3000)ppm: ± 7% of reading
  • Working humidity 0~95%RH(non-condensing)
  • Working temperature -10°C ~ 50°C

The Air Quality Guardian has a simple traffic light system 🚦 where 3 LED lights will switch on depending on the concentration of CO2 in the indoor environment. We can always view the CO2 concentration on the large display alongside the temperature (ºC/ºF), relative humidity (RH%), and histogram.

The histogram displays low and high values for all three parameters (CO2/TEMP/Humidity) and you select the desired one by navigating with the up and down arrows. Once the LOG option is selected, we can adjust the time span between 1 minute with 5-second intervals, 1 hour with 5- minute intervals, 1 day with 2-hour intervals, and 1 week with half a day intervals.

Of course, you can calibrate the device at any given moment and set alarms based on your needs. The alarm is very loud, you can’t ignore it! Interestingly, there are many alarm settings as there are some pre-established alarm settings for humans and some others for plants, yes plants. Apparently, the device can be used in greenhouses too. It supports 8 different plants (beans, chillies, cucumbers, strawberries, etc) plus one custom setting based on your needs. According to OSHA/ASHRAE, the recommended maximum level of CO2 for humans in a closed room is 1000ppm.


Once you turn the monitor on, it needs 10 seconds to warm up the sensors. The monitor responds very fast to the fluctuations of CO2. The design of the device allows air to be drawn in from the rear of the device and interact with the sensor. Consequently, it won’t easily pick up exhaled air if you are close to it. However, if you stay too much time in front of it, you will see CO2 rising.

Overall, I understand that once you connect the monitor to the power, it should be left to operate continuously. However, if you turn it off, you will lose the histogram settings but not the alarm. It would be great if it didn’t lose them.


The Air Quality Guardian must certainly be used in indoor public environments (classrooms, offices, restaurants, etc) to support the prevention and spread of COVID-19 disease thanks to the big display, traffic light system, and loud alarm. Importantly, I can also see the potential for use in professional settings like in the indoor cultivation of veggies.

Sotirious Papathanasiou

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