\nThe quality of indoor air is currently assessed based on temperature, humidity, and mainly on the concentration of carbon dioxide (CO2). However, people often complain about air quality even when all these indicators show optimal levels. This is because people’s comfort in indoor environments is reduced not only by high concentrations of CO2, but also by various odors, vapors, etc. Most of these substances that we perceive by smell (including those we cannot identify) fall into the category of so-called volatile organic compounds.
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VOC – volatile organic compounds
\nVolatile organic compounds, or VOC (from the English Volatile Organic Compounds), are chemical substances that are released as gases from solids or liquids and easily evaporate into the air at room temperature. The concentration of these substances can be up to 100 times higher indoors than outdoors.
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\nMany products that we use or are exposed to every day emit VOC into the air. These can include various cleaning agents, fumes from frying and cooking, perfumes, vapors from paints and furniture, etc. While all VOC have the potential to be harmful, there are several VOC that can be particularly dangerous and are still emitted from a range of products in our homes – such as formaldehyde, benzene, and phenol. Even slightly elevated levels of airborne chemicals can cause health problems for people, especially small children, the elderly, pregnant women, and those who suffer from allergies and asthma.
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Measuring CO2 vs. measuring VOC
\nVentilation based on carbon dioxide concentration plays an important role in managing modern ventilation systems. This gas, as mentioned, is not the only (nor the most harmful) substance in the indoor environment. Carbon dioxide itself is not dangerous to humans in small concentrations, but it is well measured, and its concentration rises in polluted spaces comparably with the concentration of other substances – which is why it was chosen as a reliable indicator for assessing air quality.
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\nReal measurements show that increased concentrations of pollutants in the air do not necessarily mean increased concentrations of CO2, and yet the air contains many health-hazardous substances. Logically, the ventilation system should respond to this situation as well, not just to the concentration of CO2.
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Sensors for monitoring indoor air quality
\nTo measure air quality not only based on CO2, “air quality sensors” are increasingly used lately, which are generally referred to as volatile organic compound sensors. These sensors are said to have measurements that approximate human perception of odors. In addition, the sensors also detect substances that people do not perceive by smell.
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\nThe wide range of detectable gases allows monitoring various gas concentrations, simplifying air quality monitoring. The detected concentration ranges from units of ppm to thousands of ppm. These features make these sensors suitable for use in low-demand spaces such as homes, social spaces, schools, gyms, etc.
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