Blog

Earth’s relatively thin atmosphere primarily consists of a mixture of nitrogen and oxygen gases. The remaining part contains inactive gases such as argon, neon, helium, hydrogen and xenon, as well as gases that vary in concentration, including water vapor, carbon dioxide, methane, nitrous oxide, ozone, airborne particles and chlorofluorocarbons.

Major air pollutants are:

• Ground-level ozone
• Carbon monoxide
• Sulfur dioxide
• Nitrogen dioxide
• Airborne particles or aerosols
• Volatile Organic Compounds

Ozone, volatile organic compounds and airborne particles are the pollutants that pose the greatest risk to human health.

Ground-level ozone is harmful to human health. It is created when sunlight reacts with certain chemical emissions such as nitrogen dioxide, carbon monoxide and methane. These chemicals can come from industrial facilities, car exhaust, gasoline vapors and other sources.

Airborne particles are solid and liquid droplets suspended in the air. They can become airborne at construction sites, smokestacks, car exhaust pipes, wildfires, volcanoes and many other places. Particles can also be formed from chemical reactions.

Particulates, also known as atmospheric aerosol particles, particulate matter, PM or suspended particulate matter, are microscopic particles of solid or liquid matter suspended in the air.

The effects of inhaling particulate matter have been widely studied in humans and animals. They include asthma, lung cancer, respiratory diseases, cardiovascular disease, premature delivery, birth defects, low birth weight and premature death.

Volatile Organic Compounds, or VOCs, are organic chemicals with high vapor pressure at room temperature. High vapor pressure is related to volatility, meaning that molecules from a material can enter the surrounding air.

Some VOCs are dangerous to human health or harmful to the environment. Aerosol products used in homes can emit harmful VOC air pollution.

Research on indoor air contamination suggests that high total VOC concentration can induce serious complaints of well-being and health. Rooms with very high VOC concentrations are not suited for the regular stay of unprotected people.

High levels of carbon dioxide may appear inside a home if ventilation is poor and indoor air does not circulate regularly. Research suggests that CO₂ levels found in bedrooms, classrooms and offices can affect the body, including cognitive performance.

Carbon dioxide levels can also reflect indoor infection risk. Tracking CO₂ levels indoors is an inexpensive and powerful way to monitor whether indoor air is being sufficiently refreshed.

One study from China reported that, of 7,324 infections, only one case with two infections was traced back to an open-air setting. This suggests that COVID-19 transmission is primarily associated with indoor environments.

Aerosols are suspensions of fine solid particles or liquid droplets in air. During breathing, exhaled aerosol particles are generated and may transport viruses out of the lungs.

Exhaled aerosol particles usually range between 0.2 and 0.6 μm. They can remain present in the room air for hours.

At a typical conversational distance, exposure to aerosols can be much greater than exposure to droplets. If an infected person is present in a room long enough, the air may become saturated with infected aerosols.

Air-conditioning devices can help spread infections because aerosols may be moved through the room within air currents, especially in rooms with poor ventilation.

Proper ventilation without recirculation can help decrease the risk of infection. Depending on circumstances, normal ventilation rates may not always be enough to reduce the risk.

UV-C technologies can help lower the risk of infection within indoor spaces. Devices such as MUONIO UV-L 110 are installed in rooms where potential infections could occur and continuously disinfect the air.

With an airflow of 120 m³/h and two concealed UV-C lamps, the unit is designed so humans can safely remain in the same space while the air is disinfected.

COVID-19 and other potentially infectious microorganisms can be treated within one air pass through the device. A room around 20–25 m² can be completely disinfected two to three times per hour.

Correct sizing matters. Some spaces have lower or higher infection risks depending on the number of people, room size, ventilation rate and other factors.

Additional reading: COVID-19 is spread by aerosols — an evidence review