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About the LuftLicht - The sensor and its measuring method

How does the LuftLicht work?

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The LuftLicht measures the CO2 content indoors via an NDIR sensor (non-dispersive infrared sensor). The sensor is mounted in the LuftLicht and receives fresh air via ventilation slots on the floor. Thus, the sensor is not exposed to a direct flow of air and therefore measures fluctuation-free and reliably. Depending on the CO2 concentration, the LuftLicht lights up green (up to 1000 ppm), yellow (between 1000 ppm and 2000 ppm) or red (above 2000 ppm), thus giving the user a clear indication on the air quality.

What is the difference between CO2 and CO2 equivalent?

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The measurement of real CO2 content in the air, requires special sensors and measuring methods, which in our case is done using the NDIR technique, in which CO2 is measured via infrared. Since these sensors are expensive, some suppliers rely on so called VOC sensors for the indoor air quality measurement. This type of sensor (often called eCO2 or TVOC sensors) measures the concentration of organic volatile compounds in the air. Under certain conditions, the readings of real CO2 and eCO2 correlate. However, an eCO2 measurement can quickly be falsified. More about this in the next section.

Why is measuring CO2 equivalent (so called V-CO2) problematic?

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CO2 monitors that measure eCO2 are problematic because these sensors also detect other gases. In particular, eCO2 measurement devices are triggered by vapors from carpets, jackets, but also deodorants or shaving lotions. The result is that eCO2 sensors indicate high levels of CO2 concentration much more frequently, as the readings are influenced by the presence of organic compounds different from CO2. Especially in classrooms with many students, it is therefore not advisable to conclude from an eCO2 value to the real CO2 concentration for indoor air quality measurement.

Functions of the LuftLicht - the calibration process

Forced calibration

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Starting with model 200001.1 S18 (see CE sticker on the bottom) you can manually calibrate the LuftLicht. This means that at any time you can reset the sensor, so to speak, and readjust it to fresh air.
- Description of the forced calibration process: First plug the LuftLicht in and leave it plugged in throughout the entire process. Turned 90° towards the charging socket is the Kensington opening, inside of which is a small button. You can press it gently with a thin object (a bent paper clip, wire, toothpick, or similar) for about 5 seconds until the light cone glows blue. Then you need to expose the LuftLicht to fresh air for 5 minutes (on the windowsill outside the window, with the window slightly closed so that the air does not mix) so that the lamp accepts this as the new reference value for fresh air and the Co2 lamp should be recalibrated.
- Below you can find an explanatory video for this Forced Calibration:

- Alternatively, you can also find the instructions in the operating manual under 14.2 (


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The instructions for this can also be found in the operating manual under 14.1. The LuftLicht recalibrates itself every 7 days. If it remains plugged in throughout and the room is thoroughly ventilated from time to time during the seven days, it should always remain freshly calibrated or recalibrate itself if necessary.

Everything about commissioning and operation (installation)

How should I operate the LuftLicht?

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Leave the LuftLicht plugged in throughout, as the sensor recalibrates itself every 7 days. Simplicity and user-friendliness were important goals in the development of the LuftLicht. We therefore decided to use a self-calibrating sensor. You don't have to carry the LuftLicht out into the fresh air or make manual setups. The only thing you must do is to give the sensor fresh air at least once a day (or air it well before the weekend).

What is the best way to mount the LuftLicht?

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The LuftLicht has a keyhole suspension on the back and can thus be mounted on the wall with a single screw. Please note the recommendation to mount the LuftLicht at a room height of approx. 1.5 meters and not directly next to a window.

Where is the best place to install the LuftLicht?

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We recommend hanging the LuftLicht at a height of 2m on the opposite side of the window.

Should I leave the LuftLicht plugged in, or should I always unplug it in the evening?

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Leave the LuftLicht plugged in all the time, as the sensor recalibrates itself every 7 days and takes the lowest CO2 value of the previous 7 days as a new reference value.

Miscellaneous/ Extras/ Adjustments/ Customer modifications

Can the LuftLicht also be operated by battery?

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We have developed the LuftLicht in close cooperation with school principals and teachers. A big disadvantage of a battery powered CO2 sensor is its maintenance. Someone must take care of checking the batteries regularly and changing them if necessary. In addition, teachers wanted the CO2 monitor to be stationary, i.e., either fixed to the wall or lockable to prevent theft. For these reasons, we have equipped our LuftLicht with a power supply unit. Since the nearest power outlet may not be a few meters away, the LuftLicht comes with an extra-long cable. If requested by the customer, we also offer the LuftLicht with a portable powerbank solution.

Does the LuftLicht have anti-theft protection?

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Yes. From our discussions with teachers and other target groups such as doctors or restaurateurs, the concern about possible theft came up again and again. We have therefore installed a device for a so-called Kensington lock (also known as a laptop lock). This allows the LuftLicht to be attached in a theft-proof manner.

Can I modify threshold values?

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Yes and no, the threshold values have been set according to the recommended CO2 values. If you nevertheless wish to have different threshold values, we can customize them for you from a certain order quantity.

Des the CO2 monitor come with a signal tone?

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No. The current version of the LuftLicht does not include a beep sound. The reason for this was that students should not be distracted as soon as the limit is reached. Much more important was the desire for a discreet but still permanently visible signal that encourages orderly ventilation. However, if you would like to order our LuftLicht CO2 monitors with a buzzer or signal tone, simply write to us at or give us a call.

Can I recalibrate the LuftLicht if I have left it in bad air for too long?

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This feature comes with the sensor due to its ability to recalibrate itself every 7 days. Just leave the LuftLicht plugged in continuously and air the room thoroughly from time to time during the week. Then the LuftLicht should always stay freshly calibrated or recalibrate itself if necessary.

Problems and miscellaneous

LuftLicht only lights up red or yellow - what to do?

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Do not panic! The LuftLicht has only calibrated itself. Starting with model 200001.1 S18 (see sticker on the bottom) you can perform a forced reset of the LuftLicht. For forced calibration and self-calibration of the older models, please read here

LuftLicht no longer illuminates

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If the LuftLicht does not light up at all, first try a different power supply. If this does not work, please contact us via

LuftLicht shines only white

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In this case you can proceed as above and recalibrate. Just blow hard into the bottom of the LuftLicht once beforehand so that it turns red.


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If you have problems with the calibration, or any other problem with your LuftLicht, we would ask you to send the LuftLicht back to us. Our workshop has been able to repair any defective AirLight so far, so none had to be thrown away.


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