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Published on Nov 6, 2014
Indoor pollutants can sometimes accumulate to levels that can pose health and comfort issues when too little outdoor air enters a home. These may include mold, bacteria, tobacco smoke, chemicals such as VOCs, radon, various allergens, elevated levels of carbon dioxide and carbon monoxide, and other pollutants.
One approach to lowering the concentration of indoor air pollutants in a home is to increase the amount of outdoor air coming in. Outdoor air enters and leaves a house by: infiltration, natural ventilation and mechanical ventilation.
With infiltration, outdoor air flows into the house through openings, joints, and cracks in walls, floors and ceilings, and around windows and doors. Air may also move out of the house in this manner and this is known as exfiltration.
In natural ventilation, air moves through opened windows and doors. Air movement associated with infiltration and natural ventilation is caused by air temperature differences between indoors and outdoors and by wind.
Finally, there are a number of mechanical ventilation devices, from exhaust (vented outdoors) fans that remove air from a single room, such as bathrooms and kitchens, to air handling systems that use fans and duct work to continuously remove indoor air and distribute filtered and conditioned outdoor air to strategic points throughout a house. The rate at which outdoor air replaces indoor air is described as the air exchange rate. When there is little infiltration, natural ventilation, or mechanical ventilation, the air exchange rate is low and pollutant levels can rise.
Unless a house is built with a means of mechanical 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. In addition, 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."
Some residential heating and cooling systems, including some forced air heating systems, do not mechanically bring fresh air into the house. Opening windows and doors, operating window or attic fans, or running a window air-conditioner with the vent control open can increase the ventilation rate. Local bathroom or kitchen fans that exhaust outdoors remove contaminants, including moisture, from the room where the fan is located.
These are just a few things to know about home ventilation and indoor air quality. To learn more about this or other environmental, health and safety issues, please visits the websites shown in the video.