Miniature sensor for good air

December 03, 2019 //By Hicham Riffi
The CO2 concentration is a key indicator of the quality of the indoor air. Good air means less drowsiness and more productivity, while too high a concentration of CO2 indoor means poor air quality, often due to inadequate air conditioning and air recirculation. This can lead to health issues including the well-documented sick building syndrome (SBS) towards which other indoor toxins can contribute, such as fine dust, mould, pollen, germs or even asbestos.

CO2 limit values prevent symptoms

The concentration of greenhouse gases and thus also the CO2 value in the environment has slowly increased over the years due to human activities; today it is slightly above 400 ppm (0.04 %) – a value that represents healthy fresh air. Indoors, CO2 values up to 1000 ppm (0.1%), which can be achieved with a good supply of fresh air, are still considered acceptable. From this concentration on, it becomes critical for health from a scientific point of view, because higher values have negative long-term effects.

Health effects of a high CO2 concentration.

Even in the range from 1000 ppm (0.1 %) to 2000 ppm (0.2 %), poor air quality is noticeable and you feel tired. From this level on, people experience the air as stuffy, and headaches, drowsiness, reduced concentration and increased heart rate can occur. Therefore, health organisations recommend keeping the CO2 value indoors below 1000 ppm (0.1%) if possible. Specifically, the EPA recommends the supply of outside air to improve the indoor air quality, for example with an HVAC system (heating, ventilation, air conditioning).


CO2 sensors indispensable in many applications

Given the large number of applications, it is not surprising that analysts expect annual double-digit market growth for CO2 sensors. CO2 sensors are used to monitor indoor air and ensure better ventilation in homes, schools, offices and commercial buildings, boosting our ability to concentrate and our productivity. Smaller sensors are also suitable for living areas and for corresponding IoT devices, such as digital assistants, smoke detectors, routers, air purifiers or air conditioning systems. Even the installation in laptops or monitors is conceivable.

Pattern recognition can be used to determine the number of people in a room and their daily activity level. This information can be used to make decisions for better air conditioning in building automation. In HVAC systems, CO2 sensors reduce power consumption by up to 50 %, which can mean energy savings of 20 % to 30 % for the entire building. In normal systems, the air circulation is kept constant in timer mode, for example during working hours. On the other hand, a control based on true CO2 measurement regulates the supply of fresh air on the basis of the actual occupancy of the room. This leads to a shorter daily duty cycle of the HVAC system and thus to considerable savings.

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