The primary cause of indoor air quality problems in homes and businesses is due to inadequate ventilation. Indoor pollutant levels increase drastically when not enough outdoor air is brought in to dilute the emissions from indoor sources & not carrying indoor air pollutants out of the home.
High temperature and humidity levels can increase concentrations of some pollutants. Another factor to consider is that 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.
There are many sources of indoor air pollution in any home. 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 household cleaning and maintenance, personal care, or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution.
Some sources, such as building materials, furnishings, and household products like air fresheners, release pollutants more or less continuously. That's why its best to use green clean or Eco-friendly products whether you are keeping house or hiring out for professional cleaning services. Other sources, related to activities carried out in the home, release pollutants intermittently. These include smoking, the use of non-vented or malfunctioning stoves, furnaces, or space heaters, the use of ozone generating air cleaners/purifiers, the use of solvents in cleaning and hobby activities, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in housekeeping. High pollutant concentrations can remain in the air for long periods after some of these activities.
If too little outdoor air enters a home, pollutants can accumulate to levels that can pose health and comfort problems. Unless they are built with special mechanical means of ventilation, homes that are designed and constructed to minimize the amount of outdoor air that can "leak" into and out of the home may have higher pollutant levels than other homes. However, because some weather conditions can drastically reduce the amount of outdoor air that enters a home, pollutants can build up even in homes that are normally considered "leaky."