Outdoor air pollution usually makes the headlines in the news, but how about the indoor air quality?

Compared to the smog in the city, indoor air pollution does not usually break the news. But with the coronavirus pandemic today, experts are calling for ways to mitigate air contaminant intrusion by upgrading the house's filter systems.

A new study suggests that outdoor air pollution, like fireworks and wildfires, can significantly impact indoor air quality. According to the Environmental Health Perspectives, over 141 million people live in areas with unhealthy levels of air pollution in the US alone. Elsewhere in the world, it could be worse, like in India and China.

But fewer people are aware of the harmful effects of air pollution indoors than outdoor air pollution. ZME Science reported that outdoor air pollution could also affect indoor air quality.

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Outdoor Air Pollution Affects Indoor Air, Proper Ventilation a Big Facto

The Relationship of Indoor and Outdoor Air Quality in Urban Buildings

According to a study on Activity patterns of Californians: Use of and proximity to indoor pollutant sources, humans spend more than 80% of their time indoors. As a result of the COVID-19 pandemic, people were forced to stay at home and work or study to prevent further transmission of the disease.

A team of researchers, led by Daniel Mendoza, studied the relationship between indoor and outdoor air quality in urban buildings. They used a network of research-grade fine PM2.5 sensors placed indoors and outdoors to quantify air pollutants' emissions.

They observed the short- and long-term relationship of indoor and outdoor air quality in Utah's Salt Lake Valley. They were able to identify three different types of elevated pollution events in their study. These are the local fireworks, seasonal wildfire, and winter inversion.

Although many people would have thought that staying indoors could protect them from the air pollution brought by these events, the study found that indoor conditions can be harmful to human health. Indoor air quality sensors reached "yellow" levels, and indoor air quality index reaching "orange" and "red" levels during wintertime inversion.

Mendoza said that this rate is not surprising given that only 20% of air pollution indoors during inversions comes directly from combustion exhaust, and the rest is secondary.

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How Do Air Pollutants From Outside Reach Indoors?

According to IQ Air, outdoor air pollutants could build up in the lower atmosphere because of temperature inversion during the cold weather when warm air rises into the upper atmosphere and traps cold air, building up air pollutants at low altitudes.

Moreover, concentrations of air pollutants could rise quickly in the mornings during rush hour as traffic levels are high but subside when traffic diminishes, and the wind and heat clear them.

Meanwhile, indoors could become contaminated with outdoor air pollutants due to the ventilation that often brings in fresh air to dilute indoor pollutants and polluted outdoor air that infiltrates indoor air.

IQ Air noted that the most common ways that indoors are contaminated with outdoor air pollutants are through open windows and doors and cracks in the walls, doors, and window sealants.

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