Indoor air quality


Indoor air quality

IAQ or Indoor air quality is not merely a matter of how the environment feels (temperature and humidity), polluted indoor air has a direct impact on our health and well-being. Depending on the degree of pollution, a poor indoor air quality can cause health problems such as respiratory diseases (e.g. asthma), allergies, and possibly even lung cancer. These symptoms are often summarised under the term SBS or Sick Building Syndromes.

Together with the increased thermal insulation of our buildings, the importance of intelligent ventilation systems is rising in order to maintain a good indoor air quality and to minimize energy losses.

The following parameters have a direct impact on the health, the sense of well-being and the comfort of the residents:

  • Temperature
  • Relative humidity
  • CO2
  • Volatile Organic Compounds

As a specialist in control solutions for HVAC and ventilation systems, Sentera developed a wide range of sensors – each with its own, specific purpose. To guide you in the process of determining the correct sensor for your application, we will explain these different parameters in detail.


Temperature and relative humidity

Temperature and relative humidity have a direct impact on the sense of well-being and comfort of the residents.

Dry air leads to dry skin, itchy eyes, and irritated nasal passages. It can cause a bloody nose or an itchy throat and can aggravate symptoms of the common cold and some respiratory ailments. It also increases static electricity, which you feel in your clothes and hair and on furniture and carpeting.

Too high relative humidity degrees will result in condensation forming on windows, walls and ceilings that are colder than the air temperature and potentially damaging building materials and causing odours in poorly ventilated spaces.

Since temperature and relative humidity are the basic parameters determining the comfort and well-being of residents, most Sentera sensors can measure these.


CO2 - NDIR CO2 sensing technology

Carbon Dioxide (CO2) is not only a by-product of combustion, it is also the result of the metabolic process in living organisms. Because carbon dioxide is also a result of human metabolism, concentrations within a building are often used to indicate whether adequate fresh air needs to be supplied to the space.

Moderate to high levels of carbon dioxide can cause headaches and fatigue, and higher concentrations can produce nausea, dizziness, and vomiting. Loss of consciousness can occur at extremely high concentrations. To prevent or reduce high concentrations of carbon dioxide in a building or room, fresh air should be supplied to the room.

NDIR is an industry term for “nondispersive infrared”, and is the most common and adequate type of sensor used to measure CO2. CO 2 gas molecules absorb the specific band of IR light while letting other wavelengths of light pass through. Finally, an IR detector reads the amount of light that was not absorbed by the CO2 molecules or the optical filter. The difference between the amount of light radiated by the IR lamp and the amount of IR light received by the detector is measured. The difference is proportional to the number of CO2 molecules in the air inside the room.

Click here to find our T, rH and CO2 sensors.

VOC- Volatile-Organic-Compounds

VOC - Volatile Organic Compounds

The human contribution to indoor air pollutants has been historically correlated with CO2, which is commonly used as an indicator for insufficient ventilation in closed spaces, but this doesn’t cover the complete load.

VOCs or Volatile organic compounds are known to cause eye, nose and throat irritations, headache, drowsiness, dizziness, nausea, difficulty concentrating and fatigue.

VOCs in indoor environments evaporate from substances such as cleaning products, adhesives, paints, new carpets, copiers and printers to building materials and furnishings. VOCs are also emitted from humans and animals in their breath, sweat and directly from their skin.

Therefore, it is important to monitor the VOC levels and to extract the contaminated air from the area.


Benefits of good indoor air quality


CO2eq - CO2 Equivalent based on the VOC measurement

  • For a more accurate indication of the indoor air quality, Sentera developed the tVOC multifunction sensors that can monitor temperature, relative humidity, ambient light and VOC levels. There is also the possibility to rescale the VOC measurement into a CO2 equivalent (CO2eq).
  • Among many VOCs, the new sensors have an increased selectivity to hydrogen (H2). In indoor environments, the H2 concentration is expected to correlate well with the CO2 concentrations as human breath contains significant concentrations of both CO2 (4 %) and H2 (10 ppm). Furthermore, humans are the major source of CO2 and H2 in typical indoor environments.
  • This makes it possible to distinguish the influence of human presence from other contaminants and control the ventilation system based on occupation of a space. Typical applications are demand based ventilation in schools, universities, office buildings, etc.
  • Click here to find our T, rH and air quality sensors.

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