In scientific terms, clean air is composed of specific gases including nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2), and water vapour. The proportion of these components can vary depending on environmental conditions. However, air also contains gases with variable concentrations, commonly known as air pollutants.
There are major air pollutants — including PM, O3, CO, and NO2 — often referred to as "criteria pollutants," due to their impact on human health and the environment. The World Health Organization (WHO) sets international air quality guidelines for these and other pollutants. For air to be considered safe, concentrations of these substances must remain below the recommended limits.
There are major air pollutants — including PM, O3, CO, and NO2 — often referred to as "criteria pollutants," due to their impact on human health and the environment. The World Health Organization (WHO) sets international air quality guidelines for these and other pollutants. For air to be considered safe, concentrations of these substances must remain below the recommended limits.
Need for Monitoring
Exposure to high levels of air pollutants has been linked to a wide range of health issues, from headaches and fatigue to more serious chronic conditions. Although it is not possible to entirely eliminate air pollutants, keeping their concentrations low is essential to protect human health.
This is where advanced air quality monitoring becomes essential. Both outdoor and indoor environments should be equipped with sensors detecting harmful pollutant levels and ensuring air quality remains within safe thresholds.
Exposure to high levels of air pollutants has been linked to a wide range of health issues, from headaches and fatigue to more serious chronic conditions. Although it is not possible to entirely eliminate air pollutants, keeping their concentrations low is essential to protect human health.
This is where advanced air quality monitoring becomes essential. Both outdoor and indoor environments should be equipped with sensors detecting harmful pollutant levels and ensuring air quality remains within safe thresholds.
The Role of Sensors
While temperature, relative humidity, and CO₂ sensors are typically used to regulate basic ventilation to ensure (thermal) comfort and supply sufficient fresh air, additional sensors measuring air pollutants play a crucial role in minimizing health risks. These sensors help detect harmful pollutants that may not be noticeable to occupants but can significantly impact long-term well-being. By integrating such sensors, ventilation systems can respond more effectively, promoting both comfort and health.
While temperature, relative humidity, and CO₂ sensors are typically used to regulate basic ventilation to ensure (thermal) comfort and supply sufficient fresh air, additional sensors measuring air pollutants play a crucial role in minimizing health risks. These sensors help detect harmful pollutants that may not be noticeable to occupants but can significantly impact long-term well-being. By integrating such sensors, ventilation systems can respond more effectively, promoting both comfort and health.
Major Air Pollutants
To gain a better understanding of air quality, it is essential to be aware of the different types of air pollutants, their sources, their chemical reactions, and their effects on human health.
To gain a better understanding of air quality, it is essential to be aware of the different types of air pollutants, their sources, their chemical reactions, and their effects on human health.
1. Volatile Organic Compounds (VOC)
Volatile organic compounds (VOCs) are chemicals that can easily turn into gases and are often found in everyday items like cleaning products, paints, varnishes, building materials, furniture, and office equipment such as copiers and printers. They are also produced by humans and animals. Additionally, they participate in the formation of ozone (O3), haze and acid rain, causing damage to the environment. The most common compounds are benzene, ethylene glycol, formaldehyde, methylene chloride, tetrachloroethylene, toluene, xylene, and 1,3-butadiene.
Volatile organic compounds (VOCs) are chemicals that can easily turn into gases and are often found in everyday items like cleaning products, paints, varnishes, building materials, furniture, and office equipment such as copiers and printers. They are also produced by humans and animals. Additionally, they participate in the formation of ozone (O3), haze and acid rain, causing damage to the environment. The most common compounds are benzene, ethylene glycol, formaldehyde, methylene chloride, tetrachloroethylene, toluene, xylene, and 1,3-butadiene.
TVOC stands for Total Volatile Organic Compounds. Monitoring TVOC levels is important because some VOCs can be harmful to our health, especially when they accumulate indoors. Breathing in high levels of certain VOCs over a long time can lead to health issues like headaches, dizziness, irritation of the eyes, nose, and throat, allergic skin reaction, and in some cases, they might even cause more serious health problems. Some VOCs are proven to be carcinogens.
The VOC index provides an overview of the total amount of VOCs in the air. It is a smart, adaptive indicator that reflects trends in indoor air pollution from VOCs. The value of 100 refers to the average indoor gas composition over the past 24 hours. While values between 100 and 500 indicate a deterioration, values between 1 and 100 inform about improvement of the VOC based air quality. The index continuously adapts to its environment and helps to detect air quality deterioration or recovery over time. This trend sensor can be used to control the fan speed of the ventilation system. When the VOC index shows a downward trend, fan speed can be reduced. In case of an upward trend, more fresh air supply is required to wash away the pollutants.
The VOC index provides an overview of the total amount of VOCs in the air. It is a smart, adaptive indicator that reflects trends in indoor air pollution from VOCs. The value of 100 refers to the average indoor gas composition over the past 24 hours. While values between 100 and 500 indicate a deterioration, values between 1 and 100 inform about improvement of the VOC based air quality. The index continuously adapts to its environment and helps to detect air quality deterioration or recovery over time. This trend sensor can be used to control the fan speed of the ventilation system. When the VOC index shows a downward trend, fan speed can be reduced. In case of an upward trend, more fresh air supply is required to wash away the pollutants.
2. Carbon monoxide (CO)
Carbon monoxide (CO) is a colourless, odourless and tasteless toxic gas. It can be freely combined with air and it is a source of fuel. It also burns with a distinguishable violet flame. Levels of carbon monoxide can be both found indoors and outdoors.
The main sources of CO indoors are unvented gas or kerosene heaters, leaking chimneys, furnaces and boilers. Additionally, there are activities that can increase the levels of CO indoors such as smoking and cooking on a gas stove. The outdoor sources of CO are vehicles or machinery that are powered by the combustion of fossil fuels. As a result, high levels of CO can be found in attached garages, parking areas and roads.
The effects of CO are hazardous to human health. Low levels of CO can cause fatigue in healthy people and chest pain in people with heart diseases, especially if they are exercising or under stress. The short-term exposure results in reduced oxygen delivery to the heart. Exposure to high levels of CO can lead to dizziness, headaches, confusion, nausea and reduced vision, coordination and brain function. The highest levels of CO are more likely to happen indoors and can be fatal to humans.
In terms of environmental impact, CO can participate in chemical reactions resulting in the creation of ozone (O3), which has a harmful effect on nature and vegetation.
Nowadays, most vehicles are designed to emit more carbon dioxide (CO2) and less carbon monoxide (CO) in the combustion of fuel. In addition, the fact that CO can react with oxygen (O2), resulting in the formation of CO2, demonstrates a direct link between CO and CO2 levels, especially in enclosed parking garages where air quality depends significantly on a proper ventilation system. The outdoor CO2 sensors of Sentera are specifically developed for accurate CO2 measurements, which can guarantee human safety in enclosed parking garages.
Sentera CO2 sensors are suitable for the measurement of air quality in enclosed parking garages. What is more, these multifunctional sen
In terms of environmental impact, CO can participate in chemical reactions resulting in the creation of ozone (O3), which has a harmful effect on nature and vegetation.
Nowadays, most vehicles are designed to emit more carbon dioxide (CO2) and less carbon monoxide (CO) in the combustion of fuel. In addition, the fact that CO can react with oxygen (O2), resulting in the formation of CO2, demonstrates a direct link between CO and CO2 levels, especially in enclosed parking garages where air quality depends significantly on a proper ventilation system. The outdoor CO2 sensors of Sentera are specifically developed for accurate CO2 measurements, which can guarantee human safety in enclosed parking garages.
Sentera CO2 sensors are suitable for the measurement of air quality in enclosed parking garages. What is more, these multifunctional sen
sors also measure temperature, relative humidity and ambient light levels. Based on the temperature and humidity measurement, the dew point is calculated. All these values are available via Modbus RTU.
3. Liquefied Petroleum Gas (LPG)
Liquefied petroleum gas (LPG) is another widely used gas by vehicles. Due to the environmental impact and state policies, the use of diesel powered engines is shrinking and is being replaced by LPG powered engines that are not that harmful to nature. LPG is used to describe two natural gas liquids: propane and butane, or a mix of the two. LPG vapour can cause fainting and choking in poorly ventilated environments.
To provide safe and healthy control of indoor air quality, a continuous gas monitoring system is necessary.
Liquefied petroleum gas (LPG) is another widely used gas by vehicles. Due to the environmental impact and state policies, the use of diesel powered engines is shrinking and is being replaced by LPG powered engines that are not that harmful to nature. LPG is used to describe two natural gas liquids: propane and butane, or a mix of the two. LPG vapour can cause fainting and choking in poorly ventilated environments.
To provide safe and healthy control of indoor air quality, a continuous gas monitoring system is necessary.
4. Particulate Matter (PM)
Particulate matter (PM) refers to a complex mixture of tiny solid particles and liquid droplets suspended in the air. The particles vary in size, shape, and chemical composition, and are classified primarily by their diameter. PM10 and PM2.5— particles with a diameter of 10 µm and 2.5 µm or less, respectively — are considered dangerous. Because of their small size, PM10 and especially PM2.5 can be inhaled into the lungs. PM2.5 particles are particularly dangerous because they can penetrate the lung’s alveoli and even enter the bloodstream, increasing the risk of serious health problems such as respiratory diseases, cardiovascular disease, and premature death.
Particles can also form acid rain that harms the environment and damages buildings and monuments. Another example of the presence of PM2.5 and PM10 in air is the formation of haze in cities. Haze leads to reduced visibility, which can result in traffic accidents since drivers are unable to see obstacles, pedestrians and other moving vehicles.
Some of the main sources of PM2.5 and PM10 are power plants and automobiles which emit chemicals such as sulphur dioxide and nitrogen oxides that are a result of complex chemical reactions. Additionally, particles are directly emitted by construction sites, fields, unpaved roads and fires. Some of the sources can be found indoors and can include activities such as smoking, cooking on a woodstove, burning food when cooking, lighting candles and fireplaces. Dust and pollen, which can enter indoor areas through open windows, are also regarded as a source of PM2.5 and PM10.
Particulate matter (PM) refers to a complex mixture of tiny solid particles and liquid droplets suspended in the air. The particles vary in size, shape, and chemical composition, and are classified primarily by their diameter. PM10 and PM2.5— particles with a diameter of 10 µm and 2.5 µm or less, respectively — are considered dangerous. Because of their small size, PM10 and especially PM2.5 can be inhaled into the lungs. PM2.5 particles are particularly dangerous because they can penetrate the lung’s alveoli and even enter the bloodstream, increasing the risk of serious health problems such as respiratory diseases, cardiovascular disease, and premature death.
Particles can also form acid rain that harms the environment and damages buildings and monuments. Another example of the presence of PM2.5 and PM10 in air is the formation of haze in cities. Haze leads to reduced visibility, which can result in traffic accidents since drivers are unable to see obstacles, pedestrians and other moving vehicles.
Some of the main sources of PM2.5 and PM10 are power plants and automobiles which emit chemicals such as sulphur dioxide and nitrogen oxides that are a result of complex chemical reactions. Additionally, particles are directly emitted by construction sites, fields, unpaved roads and fires. Some of the sources can be found indoors and can include activities such as smoking, cooking on a woodstove, burning food when cooking, lighting candles and fireplaces. Dust and pollen, which can enter indoor areas through open windows, are also regarded as a source of PM2.5 and PM10.
5. Ozone (O3)
Ozone (O3) is another air pollutant that is formed due to complex chemical reactions in the atmosphere. The major components responsible for the formation of O3 in polluted atmosphere are nitrogen (N2) and volatile organic compounds (VOCs).
The main sources of nitrogen oxides (NOx) and volatile organic compounds (VOCs) are the emissions from cars, power plants, chemical plants, electric utilities, gasoline vapours and refineries which react in the presence of sunlight creating O3. Ozone is most commonly found in urban areas, however, it can be spread through long distances by wind resulting in higher levels of pollution in rural areas as well. It is one of the main components of smog, which leads to reduced visibility and air quality.
When breathed in, O3 can cause irritation and inflammation of the respiratory system, resulting in coughing, chest discomfort and increase in asthmatic attacks for the ones suffering from the medical condition. When exposed to high levels of O3 for long periods of time, children, the elderly and individuals with respiratory illnesses are particularly prone to developing reduced lung function. Additionally, O3 can adversely affect nature and vegetation. It reduces plant growth, photosynthesis and biodiversity.
Ozone (O3) is another air pollutant that is formed due to complex chemical reactions in the atmosphere. The major components responsible for the formation of O3 in polluted atmosphere are nitrogen (N2) and volatile organic compounds (VOCs).
The main sources of nitrogen oxides (NOx) and volatile organic compounds (VOCs) are the emissions from cars, power plants, chemical plants, electric utilities, gasoline vapours and refineries which react in the presence of sunlight creating O3. Ozone is most commonly found in urban areas, however, it can be spread through long distances by wind resulting in higher levels of pollution in rural areas as well. It is one of the main components of smog, which leads to reduced visibility and air quality.
When breathed in, O3 can cause irritation and inflammation of the respiratory system, resulting in coughing, chest discomfort and increase in asthmatic attacks for the ones suffering from the medical condition. When exposed to high levels of O3 for long periods of time, children, the elderly and individuals with respiratory illnesses are particularly prone to developing reduced lung function. Additionally, O3 can adversely affect nature and vegetation. It reduces plant growth, photosynthesis and biodiversity.
6. Nitrogen dioxide (NO2)
Nitrogen dioxide (NO2) belongs to a group of highly reactive gasses called nitrogen oxides (NOx). Nitrogen dioxide (NO2) is formed in combustion processes involving nitrogen and oxygen. The main factor for the presence of NO2 in air is the burning of fuel. In this sense, emissions from power plants, vehicles, industrial activities and residential heating play a key role in NO2 levels. In addition, enclosed parking garages require proper ventilation since vehicles produce emissions that are hazardous to health. In this case, the detection of CO2 can be used as criteria for the overall safety of the enclosed parking garages since huge amounts of CO2 are emitted in the combustion of fuel. The CO2 sensors of Sentera are specifically designed to detect CO2 levels, ensuring that they are within a safe range. As a result, Sentera outdoor CO2 sensors are a key element of any ventilation system in enclosed parking garages.
Nitrogen dioxide has damaging effects on human health. Exposure to high levels of NO2 over short periods can result in irritation and inflammation of the airways in the human respiratory system. Symptoms such as coughing, difficulty breathing and wheezing may occur.
There also exists an environmental effect of NO2. Nitrogen dioxide in combination with water, oxygen and other chemicals forms acid rain. Moreover, NO2 reacts with other air pollutants creating smog and damaging air quality.
Nitrogen dioxide (NO2) belongs to a group of highly reactive gasses called nitrogen oxides (NOx). Nitrogen dioxide (NO2) is formed in combustion processes involving nitrogen and oxygen. The main factor for the presence of NO2 in air is the burning of fuel. In this sense, emissions from power plants, vehicles, industrial activities and residential heating play a key role in NO2 levels. In addition, enclosed parking garages require proper ventilation since vehicles produce emissions that are hazardous to health. In this case, the detection of CO2 can be used as criteria for the overall safety of the enclosed parking garages since huge amounts of CO2 are emitted in the combustion of fuel. The CO2 sensors of Sentera are specifically designed to detect CO2 levels, ensuring that they are within a safe range. As a result, Sentera outdoor CO2 sensors are a key element of any ventilation system in enclosed parking garages.
Nitrogen dioxide has damaging effects on human health. Exposure to high levels of NO2 over short periods can result in irritation and inflammation of the airways in the human respiratory system. Symptoms such as coughing, difficulty breathing and wheezing may occur.
There also exists an environmental effect of NO2. Nitrogen dioxide in combination with water, oxygen and other chemicals forms acid rain. Moreover, NO2 reacts with other air pollutants creating smog and damaging air quality.
Conclusion
Maintaining clean air is a complex challenge influenced by many factors, making continuous air quality monitoring essential to ensure human health and safety—particularly indoors. Moreover, public buildings must strictly adhere to ventilation regulations designed to uphold air quality standards. These regulations establish critical safety thresholds that must never be exceeded to guarantee that the air remains safe for all occupants.
Maintaining clean air is a complex challenge influenced by many factors, making continuous air quality monitoring essential to ensure human health and safety—particularly indoors. Moreover, public buildings must strictly adhere to ventilation regulations designed to uphold air quality standards. These regulations establish critical safety thresholds that must never be exceeded to guarantee that the air remains safe for all occupants.