Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of building occupants. Poor indoor air quality has been linked to sick building syndrome, reduced productivity, and impaired learning in schools. Common pollutants of indoor air include: Secondhand tobacco smoke, air pollutants from indoor combustion, radon, molds and other allergens, carbon monoxide, volatile organic compounds, legionella and other bacteria, asbestos fibers, carbon dioxide, ozone and particulates. Source control, filtration, and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality in most buildings.

Determination of IAQ involves the collection of air samples, monitoring human exposure to pollutants, collection of samples on building surfaces, and computer modelling of air flow inside buildings. IAQ is part of indoor environmental quality (IEQ), which includes IAQ as well as other physical and psychological aspects of life indoors (e.g., lighting, visual quality, acoustics, and thermal comfort).

Indoor workplaces are found in many working environments such as offices, sales areas, hospitals, libraries, schools and preschool childcare facilities. At such workplaces, no tasks involving hazardous substances are performed, and they do not include high-noise areas. Nevertheless, employees may feature symptoms belonging to the sick building syndrome such as burning of the eyes, scratchy throat, blocked nose, and headaches. These afflictions often cannot be attributed to a single cause, and require a comprehensive analysis besides the testing of the air quality. Factors such as the workplace design, lighting, noise, thermal environment, ionising radiation and psychological and mental aspects have as well to be allowed for. A report assisted by the Institute for Occupational Safety and Health of the German Social Accident Insurance can support in the systematic investigation of individual health problems arising at indoor workplaces, and in the identification of practical solutions.

Indoor air pollution is a major health hazard in developing countries and is commonly referred to as "household air pollution" in that context. It is mostly relating to cooking and heating methods by burning biomass fuel, in the form of wood, charcoal, dung, and crop residue, in indoor environments that lack proper ventilation. Millions of people, primarily women and children face serious health risks. In total, about three billion people in developing countries are affected by this problem. The World Health Organization (WHO) estimates that cooking-related indoor air pollution causes 3.8 million annual deaths. The Global Burden of Disease study estimated the number of deaths in 2017 at 1.6 million.

In January 2023, suggestions for decreasing indoor air pollution when using a gas stove, which is linked to an increased risk of asthma and other possible illnesses, were published in The New York Times.