Always enough fresh air

with CO2 monitoring


Fresh air is good for everybody, and our bodies need oxygen to function properly. Fresh air means nothing more than good quality of air combined with a low level of CO2. The quality of air is measured in ppm. ‘ppm’ stands for ‘parts per million’, here referring to the percentage of CO2 in the air. The DIN 1946 standard sets the maximum value for ventilation at 1500 ppm.

In comparison: fresh air outside has no more than 350 to 500 ppm. In a flat, this value is typically between 500 and 1000 ppm, 800 ppm being a good level here. Bad air is essentially used-up air. If the CO2 value exceeds 1000 ppm, the room should be ventilated. If the value exceeds the 2000 ppm limit, ventilation is required, as this already poses a health risk.

The climate at home or in the office can have a significant impact on physical health, productivity and general well-being. CO2 propagates very quickly, especially in small rooms, exceeding the recommended range between 800 and 1000 ppm. Bedrooms and living rooms are often affected as well, as they are ventilated rather irregularly, or much too little.

Recognising an increased level of CO2

·         Headaches or dizziness, general discomfort

·         Tiredness, lack of productivity or strength (when over 1000 ppm)

·         Difficulty concentrating (when over 1500 ppm)

·         Strong cough reaching shortness of breath or even unconsciousness. This is particularly hazardous for people with asthma, as it significantly increases the breathing rate. High levels of CO2 in the air ‘poison’ the body, as it expels oxygen from the circulating blood, preventing its supply to the cells of the body.

The first thought that comes to one’s mind here probably is: as soon as the room is ventilated, it will have enough fresh air again. The CO2 concentration does indeed fall with ventilation, preventing immediate harm to well-being. The difficulty here is to determine the precise level of CO2, which is exactly what one needs to know! And it is in this situation where one uses smart building technology with CO2 sensors.

Knowing when there is too much CO2 in the room

With the right building technology, you can constantly monitor the CO2 concentration effortlessly. Thanks to the automated ventilation function, this is not only comfortable, but also energy efficient. Elsner Elektronik offers various CO2 sensors as individual devices or combination devices for various systems.

The compact AQS/TH-PF ventilation controller does not need a bus system and is an option for use in any building. The combination device with sensors and control equipment automates ventilation through windows/ventilation devices and indicates the exact CO2 value on the display. It is easy to integrate in the switching software of the building and to connect with the window/ventilation device. CO2 measurements and automated ventilation can be made very simple!

CO2 measurement in buildings equipped with KNX bus technology can be implemented using, for example, the KNX AQS/TH-UP gl and KNX AQS/TH-UP Touch wall sensors. They combine different functions, including temperature and humidity measurement, as well as CO2 measurement. If windows or ventilation devices can be controlled by KNX actuators, the sensors can order the automatic opening/closing of the windows and the switching on/off of the ventilation, to keep the quality of air in the room at a pleasant level of under 1000 ppm. And do not worry: opening the windows for ventilation at night can be prevented through manual time settings. You can also use the timed switching function, so that the particularly cool and fresh air fills the room in the morning, for example.

Another option in visually representing the CO2 content is offered by the Corlo Touch KNX room controller. The display can also provide the exact value or indicate a text-based alert for ventilation. The integrated ambient lighting of the device can furthermore be used, which, for example, changes to red, to make the bad quality of air more noticeable.

The Sewi KNX AQS sensor, which is purely a CO2 sensor, is suitable for discreet installation on the ceiling. The device controls ventilation using, for example, windows equipped with KNX actuators. This sensor also has an option for communication via the Modbus data protocol.

Room air plays a role everywhere

There are different ways of measuring the CO2 value: from a ventilation recommendation to automated ventilation, individual controls and an entire KNX system. There is a custom solution to every project. It is important to be aware of the fact that the concentration of CO2 is an important factor for well-being and human productivity be it in private, public or industrial buildings, and it should not be left without attention.


Further sources: Publication ‘Health assessment of carbon dioxide in interior air’ (‘Gesundheitliche Bewertung von Kohlendioxid in der Innenraumluft’) by Federal Environment Agency (2008).



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