It may come as a surprise but air pollution levels indoors are almost always higher than outside, even in busy city centres. Even more surprising is that indoor plants have the ability to mitigate high levels of most airborne contaminants.
Ventilation systems constantly "refresh" buildings with air from outdoors after a filtration process that removes some large particles, such as pollen, from it. Once inside, this air is augmented by a large range of indoor-sourced pollutants.
Two of the most significant of these are volatile organic compounds (VOCs) and carbon dioxide.
Volatile organic compounds are petrochemical vapours that are "outgassed" or continuously liberated from building materials, such as paint and carpet, as well as furnishings, plastics and electronic equipment. In high concentrations, many of these agents are acutely toxic and carcinogenic. Some even disrupt the endocrine systems of animals.
While the concentration of volatile organic compounds in modern buildings is generally quite low, there's growing evidence that continued chronic exposure to even low levels of these chemicals may result in the condition known as sick building syndrome.
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