There are many sources of indoor air pollution in any commercial building. These include combustion sources such as oil, gas, kerosene, coal, wood, and tobacco products; building materials and furnishings as diverse as deteriorated, asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for cleaning and maintenance; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution.
The relative importance of any single source depends on how much of a given pollutant it emits and how hazardous those emissions are. In some cases, factors such as how old the source is and whether it is properly maintained are significant. For example, an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted.
Some sources, such as building materials, furnishings, and household products like air fresheners, release pollutants more or less continuously. Other sources, related to activities carried out in the office or related building spaces, release pollutants intermittently. These include smoking, the use of unvented or malfunctioning furnaces, or space heaters, the use of solvents in cleaning, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in cleaning and maintenance. High pollutant concentrations can remain in the air for long periods after some of these activities.