Clean Your Home's Air with a Central Air Filter
Truly effective air filters are available in a couple of designs. Your two primary options are freestanding portable room filter systems, and central air filters that work in conjunction with your furnace and central air conditioner. The little desktop units that are sold as air filters just don't have the power to move enough air to provide effective filtering of the air in a room.
Pros and cons of a central air filtration system
A central system has a number of advantages. They are out of sight (integrated into your home heating system, usually by the furnace), very convenient (you'll never trip over one), and they are quiet when they're operating.
However, central systems only work when the HVAC is operating, so they don't usually provide continuous air filtration, which makes some experts question their effectiveness as opposed to dedicated room air filters. Since ductwork may need to be modified for an add-on unit, a heating or mechanical contractor is usually required to install them. Also, central air filters are relatively expensive, with installed prices for systems being in the range of $1500 to $2500.
How do they work?
A central air filtration system provides whole house air filtration by filtering the air as it cycles through the air ducts into the furnace. Over time, all the air in the house will pass through the system, and it will be cleaned and filtered each time it passes.
Types of central air filtration
A regular furnace filter provides a form of air filtration, although not a very efficient one. The standard spun glass furnace filter is estimated to remove about 10 percent of the particulate matter in the air. At a price of about $1.00 each, they provide inexpensive filtering of the largest dust particles.
Pleated air filters, which also are designed to fit into the furnace filter slot, provide better air filtering. Manufactured from heavy paper fan folded to form a pleated surface, they capture 30 to 40 percent of airborne particles. Slightly more expensive than standard glass filters at about $10.00 each, one will filter the air in your home for about two months before they need to be discarded.
Electrostatic air filters are the most effective technology for filtering your home's air. These use electronically charged filters to attract and hold dust allergens and other irritants. An electrostatic air filter is much more effective than a standard or pleated air filter, and as a bonus, the filter can be cleaned and reused. While electrostatic air filters are available that will fit into the furnace filter slot, the most effective filters are too large to fit the slot and generally require some retrofitting of the ductwork so they can be integrated into the HVAC system.
What's a HEPA filter?
A true HEPA (High Efficiency Particulate Air) filter is also known as an absolute air filter because of its high efficiency. HEPA filters were developed during World War II by the Atomic Energy Commission to capture radioactive dust particles that might present a health hazard to the researchers. True HEPA filters operate with a minimum efficiency of 99.97 percent when tested with particle sizes 0.3 microns or smaller. Just to put that in perspective, a micron is one millionth of a meter, and a particle that is 10 microns in size is not visible to the human eye. A human hair is 70 to 100 microns in width.
Because of their high efficiency, true HEPA filters are expensive. However, HEPA-like filters are available for home use. While not as efficient as a true HEPA filter, they do remove a high percentage of airborne particles. Based on their high efficiency, HEPA and HEPA-like filters are usually built with one or even two pre-filters. The function of the mechanical pre-filters is to remove larger particles before they reach the HEPA filter, so it doesn't become clogged.
What about cleaning air?
Air filter systems are designed to capture airborne particles; they themselves don't "clean air." However, some air filtration systems do include ozone generators or Ultraviolet light components designed to actually kill airborne bacteria.
Ozone is a highly reactive chemical that some claim will render harmless any chemical contaminant. However, people with Asthma are highly sensitive to ozone and it can even trigger attacks. The American Lung Association does not recommend using air filters that generate ozone.
UV lights have been used in medical and laboratory environments to help eliminate bacteria and mold. The lights lose effectiveness over time, and need to be replaced about once a year. At a cost of about $100 each, their value would depend on your individual situation.
The air filtration system that is right for you will obviously depend on your own requirements. If dust control is your primary concern, upgrading your regular furnace filter to a pleated filter may be all you need. However, if you or someone in your family suffers from allergies or Asthma, an electrostatic air filter would seem to be the better option.