How Humans Affect Indoor Air

November 2, 2021

Humans emit significant amounts of chemical compounds indoors. Several studies published by scientists at the Max Planck Institute for Chemistry now show the extent to which we influence the air in enclosed spaces.

The human body can have a strong impact on the chemical composition of indoor air. Through our skin and our breath, we emit a complex mixture of compounds that can react in the environment. Not only outdoor air pollution plays an important role in human health, but indoor air quality as well, as we spend most of our time indoors, and this has increased since the coronavirus pandemic. Although buildings protect us to some extent from outdoor pollution, they increase our exposure to chemicals generated in the home. This is why it is especially important to understand how human emissions affect the composition of indoor air.


An international team of scientists led by the Max Planck Institute for Chemistry has carried out a series of experiments to analyze and identify the exact nature and chemistry of human emissions indoors. The results have recently been published in five scientific articles.

“What we have studied is the total profile of human trace gas emissions and what specific compounds come from the skin and breath,” says Jonathan Williams, group leader at the Max Planck Institute for Chemistry. The scientific team measured for the first time the total reactivity of human emissions and verified their sensitivity to the presence of ozone, one of the most important oxidants indoors. “When ozone reacts with the oils in the skin, it releases many reactive compounds. Just by opening the window, we let in more ozone and generate more of these reactive compounds in the air, ”explains Williams. It is necessary to continue investigating what influence these substances have on the human body.

Another aspect the scientists focused on during their experiments were large biological particles and ammonia from the skin. “When clothing rubs against our skin, we release particle flakes into the air, and the warmer we are, the more ammonia comes out of the skin,” Williams explains. If we keep the house cool and wear long pants and shirts, we add our own particles to those that enter from the outside, while if we raise the thermostat and wear T-shirts and shorts, we will emit much more ammonia and alter the pH of the surfaces of our house . The results make it clear that the way we choose to live influences our inner chemistry.

Scientists see a great need to investigate the relationship between outdoor air pollution and indoor air composition. As the air enters a building, the size distribution within the aerosol changes and the particles that remain in the air can capture the chemicals released inside to be transported deep into the lungs. Also, temperature, humidity, and chemicals in indoor air can change the composition of fine particles in ways that are not well understood.

The experiments were conducted in a climate-controlled stainless steel chamber occupied by four people at the Technical University of Denmark. The participants wore special clothing washed with an unscented detergent. The scientists made measurements by varying the temperature, relative humidity, age of the people, and the amount of ozone in the chamber, as well as the type of clothing the participants wore.

The team surrounding Jonathan Williams is scheduled to return to the Copenhagen climate chamber for another series of experiments later this year. During this new campaign they will explore how human emissions change when exercising, as well as in relation to personal hygiene. In addition, scientists will comprehensively measure the changes in emissions that occur when participants wear a mask. “Today we all wear masks, so it is important to see how face coverings influence the chemistry of the indoor air around us,” adds Williams.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
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