Air Quality

The terms ambient air, ambient air pollution, ambient levels, ambient concentrations, ambient air monitoring, ambient air quality, etc. occur frequently in air pollution parlance. The intent is to distinguish pollution of the air outdoors by transport and diffusion by wind (i.e. ambient air pollution) from contamination of the air indoors by the same substances.

The air inside a factory building can be polluted by release of contaminants from industrial processes to the air of the workroom. This is a major cause of occupational disease. Prevention and control of such contamination are part of the practice of industrial hygiene. To prevent exposure of workers to such contamination, industrial hygienists use industrial ventilation systems that remove the contaminated air from the workroom and discharge it, either with or without treatment to remove the contaminants to the ambient air outside the factory building.

The air inside a home, office, or public building is the subject of much interest and is referred to as indoor air pollution or indoor air quality. These interior spaces may be contaminated by such sources as fuel‐fired cooking or space‐heating ranges, ovens, or stoves that discharge their combustion products to the room; by solvents evaporated from inks, paints, adhesives, cleaners, or other products; by formaldehyde, radon, and other products emanating from building materials; and by other pollutant sources indoors. If some of these sources exist inside a building, the pollution level of the indoor air might be higher than that of the outside air. However, if none of these sources are inside the building, the pollution level inside would be expected to be lower than the ambient concentration outside because of the ability of the surfaces inside the building – walls, floors, ceilings, furniture, and fixtures – to adsorb or react with gaseous pollutants and attract and retain particulate pollutants, thereby partially removing them from the air breathed by occupants of the building. This adsorption and retention would occur even if doors and windows were open, but the difference between outdoor and indoor concentrations would be even greater if they were closed, in which case air could enter the building only by infiltration through cracks and walls.

Many materials used and dusts generated in buildings and other enclosed spaces are allergenic to their occupants. Occupants who do not smoke are exposed to tobacco and its associated gaseous and particulate emissions from those who do. This occurs to a much greater extent indoors than in the outdoor air. Many ordinances have been established to limit or prohibit smoking in public and workplaces. Attempts have been made to protect occupants of schoolrooms from infections and communicable diseases by using ultraviolet (UV) light or chemicals to disinfect the air. These attempts have been unsuccessful because disease transmission occurs instead outdoors and in unprotected rooms. There is, of course, a well‐established technology for maintaining sterility in hospital operating rooms and for manufacturing operations in pharmaceutical and similar plants.