Particulate matter (PM) is made up of a number of components, including acids, organic chemicals, metals, soil or dust particles, and biological contaminants. Coarse particles tend to settle in the upper respiratory tract, and large particles can be trapped in the nose and throat and be expelled by coughing, sneezing, or swallowing.
Respirable particles are directly emitted into indoor air from a variety of sources including tobacco smoke, ozone reactions with emissions from indoor sources of organic compounds and flues improperly installed or maintained, unvented appliances such as gas stoves or gas space heaters, woodstoves, and fireplaces. These particles also include viruses, bacteria, mold fragments, spores and a significant fraction of cat and dog dander.
Gaseous pollutants include combustion gases and organic chemicals that are not attached to particles. Hundreds of gaseous pollutants have been detected in indoor air.
Sources of indoor combustion gases include combustion appliances, tobacco smoke, and vehicles whose exhaust infiltrates from attached garages or the outdoors, as well as the sources of airbone gaseous organic compounds. These ones may also come from cooking food; from human, plant, and animal metabolic processes; and from outdoor sources.
Two strategies to reduce indoor air pollutants
Source control eliminates individual sources of pollutants or reduces their emission. It is usually the most effective strategy for reducing pollutants. Solid wood can be used and is likely to be a significant source of formaldehyde. Smokers can smoke outdoor and combustion appliances can be adjusted to decrease their emissions.
Ventilation exchanges air between the inside and outside of a building. The introduction of outdoor air is important for good air quality. Natural ventilation through open windows and doors is a method that can also be used in most homes. In a process known as infiltration, outdoor air flows into the house through openings, joints, and cracks in walls, floors, and ceilings, and around windows and doors.