Leaving Your Fan On
by Building Inspector and Indoor Air Specialist, Dan Schilling
© Copyright 2002 Residential Inspections LLC, All Rights Reserved
Understanding Your Fan
If you have a forced air system that moves air through air ducts in your home, you probably have a thermostat that has a switch on it with two positions, “On” or “Auto”. When in automatic mode, your blower fan will only come on when your system calls for heat or air conditioning. When the switch is in the on position, your fan will run constantly to circulate air around your home, whether or not you are heating or cooling. Turning the fan switch on your thermostat to the “on” position can benefit those with allergies, asthma or any other indoor air related illness. This strategy also benefits those who have not yet experienced indoor air symptoms.
Provided that you are using a high-quality air filter in your heating/cooling system, running the fan converts your air handling system into an air filtering system which continuously scrubs the air throughout your entire home. Due to the air flow directly from the supply registers back toward the return registers, there will be areas of stagnant air in rooms which does not pass through the air ducts (necessitating ion replacement). However, enough air does pass through the air duct system to easily justify the nominal cost of running the fan for the added filtration benefits.
If you are using an air purification system that replaces the electrical ions in your indoor air, operating the fan will be enhanced even more. Without ions, sub-micron particles in the indoor air can easily pass right through the best of air handling system filters and then be re-circulated throughout the house. These ultra fine particles are the ones which are the most detrimental to our health. With an ionizing air purifier, the airborne particles become enlarged through ionic coagulation of the smaller particles, allowing them to be captured in the filter.
There are two additional benefits for those who operate their fans continuously: The increased air circulation will help to minimize stagnant air around the house which in turn will provide a more balanced air temperature throughout the rooms. This is particularly beneficial for homes with two or more levels. Finally, the visible dust that settles around the house will be significantly reduced, thereby reducing the manual labor of dusting.
Frequent Filter Cleaning or Replacement
If using your air handling system as an air filtration system, you must remember to replace or clean your air filters more often due to the increased dust load. It is recommended to write the times for filter replacement or cleaning onto your calendar, to be certain this is not overlooked. Unless you are using a wide cartridge-type filter, which is rated for an entire year, you probably will be using standard, one inch filters, which should be replaced or cleaned once a month. This can depend largely on the dust load created in your home. If you have pets or children running around the house or if there are cigarette smokers in the house, you may need to check the filters on a more frequent basis. The general rule is that if there is not a visible layer of dust on the filter and sufficient air is still passing through the filter, don't change or clean them just yet. A little dirt can actually make the filter more efficient.
Caution When Cleaing or Replacing Filters
Whether using disposable or re-useable filters, always be careful when removing them. If filters are yanked out fast or bumped, many of the particles they have collected can be dislodged and will be immediately redistributed in the indoor air. The amount of allergens, bacteria and viruses on these filters can be massive and extreme caution should be taken when changing or cleaning the filters. A disposable filter should be placed immediately into a plastic trash bag or very carefully carried outdoors. If placed un-bagged into a garbage can and anything is subsequently tossed on top of it, many of the trapped particles will be re-distributed into the air. If the more efficient electrostatic-type filters are used, they can be washed or vacuumed for cleaning, but require caution as well. They can be washed outdoors with a garden hose or indoors in a bath or utility tub. If washing indoors, be careful not to dislodge the dust by bumping the filter before washing it. If you will be vacuuming the filter off, it is recommended to do so outdoors, or to make sure that the vacuum being used has allergenic HEPA filtration to prevent the particles from being redistributed indoors.
The Noise Factor
Depending on the design of your air ducts and the size or speed of the blower, a few people may find the sound of the air continually moving through the ducts undesirable. If this is the case, it is possible to operate the fan only while sleeping, at work, or during periods of heavy dust creating activity. The fan can then be switched back to the auto position during those periods of time when the sound level is a factor.
with those you care about.