Filterless Air Cleaning?

The majority of aircleaners sold as not needing replacement air filter media are electronic: electrostatic precipitators. This category includes market volume leaders Ionic Breeze, Oreck air purifier, and Friedrich C90 air cleaners, as well as a host of imitators. These machines electrically charge airborne impurities and then gather them on an oppositely charged plate. So where does the accumulated mess go? Inside the air purifier! Most of it is deposited on the metal collection plates or grids.

These collectors must be washed often, or they begin to let uncleaned air slip past. Over time, especially where there is oily residue from cigarette smoking or grease frying, the plates build up an oxidized film layer. This can be very difficult to remove. When this insulation builds up, forces of attraction diminish, leading to bypassing and lowered efficiency. Particles may also adhere to the inner parts of the machine, blowing out when it is turned on. So filterless air cleaners sometimes end up being the filter.

Ionizing wires or brushes wear down or sludge up, requiring additional maintenance.

Many electrostatics have ozone emissions which crowd the .050 parts per million standard.

Electrostatic filtering has no ability to remove chemicals or odors. Ozone will do this, which is why many top sellers continue to produce ozone despite negative publicity. If they stopped generating ozone, would their air purifiers continue to please users?

Some electrostatic builders add prefilters and carbon pad postfilters to compensate for the above defects. By doing this, they are no longer filterless air purifiers. Filterless benefits are partially eliminated, since these added filters can be pricey.

So leading electrostatic "filterless" air cleaning devices may actually have filters, or have problems and limitations not featured in advertising.

Air purifiers using ionization alone may not rely on air filtration. While many air purification products are marketed as "ionic", true ionizers just emit ions into the air. These gather airborne particles into clumps which grow until they fall to the floor or stick to walls, draperies, or furniture. While these air purifiers are filterless, the dirt is not removed permanently. It will become airborne again soon. Ionizers gather only particles, so unless they have high ozone emissions there is no chemical/odor filtering. Some ionic air purifiers are fanless, so they rely on room drafts and convection to move air.

The air purifying technology which may put filterless air purification on the map is photocatalytic oxidation (PCO). No filters are necessary for PCO systems, which may be as simple as a single coated florescent light bulb. Ultra violet light excites metal semiconductors, which produce oxidants capable of destroying smaller particulates, chemicals, and odors. Since the tiniest particles are the deadliest and most difficult to filter conventionally, PCO is a real breakthrough. While PCO can actually be filterless, filters are usually added to capture the larger particles.