Review: Aranet4 HOME Wireless Indoor Air Quality Monitor

aranet4 Air Quality Sensor

We’re always interested in Air Quality sensors and the latest one to turn up at the Automated Home is the Aranet4.

This is the first domestic indoor air quality sensor from the sub-brand of the Latvian company SAF Tehnika. It measures Carbon Dioxide (CO₂), Temperature, Relative Humidity and Atmospheric Pressure.


The stand out feature of this device is its ability to show all its measurements on screen. Using tech similar to the Eve Room, the display employs an e-ink screen which provides an informative, if a little small, panel of readings.

The advantage of this type of display is its low power requirements and its high contrast is easily read if there’s good ambient lighting. The unit can sit on table or shelf, or be wall mounted if you prefer.


There’s no VOC or PM2.5 detectors here, but the on-board electronics use a special type of ‘NDIR’ sensor for CO₂ measurements…

Aranet4 uses non-dispersive infrared (NDIR) sensor for measuring the CO₂ level. The device has a small gas chamber with infrared light source in which CO₂ absorbs the light. An optical filter in front of a detector then filters all of the light except the wavelength that the CO₂ molecules can absorb so a precise measurement of the CO₂ level can be made.

As well as the integer display the screen also shows a 3 colour traffic light system. The maximum indoor CO₂ level considered acceptable is 1,000 parts per million and the colours mean the following:

  • Green – good (below 1,000 ppm). Optimal indoor air quality
  • Yellow – average (1,000 ppm). Brain cognitive function lowers by 15%
  • Red – unhealthy (1,400 ppm). Brain cognitive function drops by 50%
Aranet4 at the Automated Home 2.0

There’s an audible warning buzzer that can be enable or disable as an alarm for dangerous levels. It’s recommended that you calibrate the device once per year and this can be done automatically or manually.

You can select measurement to be recorded every 1, 2, 5 or 10 minutes and Aranet say this will be the difference between your batteries lasting from 4 months to 2 years.

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It’s worth pointing out that the unit warns that inserting the batteries incorrectly will damage it badly enough to mean it needs to be returned to the manufacturer for repair. The FAQ also warns that a drop could permanently damage the sensor too, so be careful.


There’s an Android and iOS app which is a little basic currently, we’d like to see this develop and improve over time.

Some features can be controlled from the app while other are only accessible via dip switched that are under the cells in the battery compartment.

1) default measurement interval is set to 5 minutes;
2) CO2 sensor automatic calibration is disabled;
3) default temperature measurement units are set to Celsius;
4) Bluetooth connection is enabled;
5) Bluetooth connection transmission range is set to normal;
6) Buzzer for audio sound alarm notifications is disabled;
7) CO2 indication is set to human mode;
8) Access to Homey Smart Home assistant is enabled.

The 2nd, 3rd and 4th setting can be changed with the switches in the battery compartment on the back of the device, but the remaining five settings can only be changed via the Aranet4 phone application.

The app works in portrait mode but turning it to landscape gives a wider view where you can pinch to zoom-in on your data.

Aranet4 App


There’s an unofficial Web API and a Python client and library available if you want to try some DIY integration and the sensor works with Homey too.


Rating: 4 out of 5.

The Aranet4 is a neat little air quality monitor with high grade CO₂ sensor.

Its USP is its ability to show you real time readings at a glance, without having to get your phone out of your pocket to launch an app.

Available now.

Available from Amazon

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Last update on 2024-04-08 / Affiliate links / Images from Amazon Product Advertising API

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