As you can see, if the pleated filter media was stretched out straight, the pleated filter has 2 to 3 times more surface area.
The Media filter
The next step up in air filtration is the 4" or 5" thick media filter.
These filters are in-line between your furnace, or air handler, and the return air ducting. 100% of the air circulating through your comfort system passes through this filter.
The media filter uses no electricity and actually becomes more efficient as the media nears replacement time (gets dirtier).
Some media air filtration systems boast as high as being 95% efficient at trapping and removing particles as small as 1 micron.
The replacement filters are readily available at your local home improvement store, or from your hvac contractor.
Electronic air cleaner
The old familiar electronic air cleaner is still around. It installs between your air handler and return ducting, where 100% of the air being circulated goes through this unit. Pre-filters grab the largest particles. The rest pass through electrically charged cells, which attract the particulates, zap them with an electrical charge, effectively killing the enemy.
The cells inside this unit can be cleaned by running them through your dishwasher.
Some of these units claim 94% effectiveness on particulates down to .35 micron.
WARNING: Make sure the cells are completely dry before reinstalling in the air cleaner cabinet.
Multi-media filtration w/UV
Other variations of the inline whole-house air cleaner are becoming very popular. A popular alternative to the electronic air cleaner is a media air cleaner with a 1" media pre-filter, a high MERV-rated 4" or 5" media filter with an integral ulta-violet light built into the cabinet. The germicidal ultra-violet light irradiates and kills living bacterial organisms in the air stream before the air is redistributed back into the home.
These units also claim to be highly effective at controlling and neutralizing common odor causing pollutants, such as cooking odors, pet odors, smoking, and other lingering odors.
The pre-filters should be replaced once per month, the 5" media filter twice per year, and the UV light should be replaced once per year. Your contractor should be able to supply you with 1-year service packs for these units.
Passive HEPA air filtration system
Another style of high efficiency air cleaners is the passive, or "partial bypass", configuration. This type sits to the side of your air handler and is ducted into the return ductwork in 2 locations.
This unit cleans a percentage of your indoor air at all times, if you have your thermostat set on fan. This unit is especially effective as an addition to a variable speed furnace or air handler.
Stale contaminated air is drawn into the unit, passes through a pre-filter and then a HEPA filter, before passing by the ultra-violet light, and then is redistributed back into the home.
99.97% of airborne particulates as small as 0.3 micron are captured and killed. These units have their own blower, which can provide 50-75 clean air changes per day.
I like this style of air filtration because it can be installed on just about any configuration of forced air system, without need to alter the ducting to fit it in.
Every manufacturer of hvac equipment produces their own version of all of these air filtration systems. Many variations are available, and each supplier and manufacturer thinks his product is better than the other guys.
The fact of the matter is, all of the air cleaners and air filters you have just read about will improve the air you breathe in your home. The choices are limitless. The variations, styles, manufacturers and suppliers are limitless. To make recommendations would probably add 4 pages here.
I believe that I will leave the final choice to you and your hvac contractor.
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