Filterless Air Purifier?
Many people find the "filterless" air purifier or air cleaner concept attractive.
The problem is that many filterless air cleaners filter less!
A central vacuum system can just blow the dirt outside, but air purifiers without filters must do something with the material removed from the air.
The air purification market is filled with shameless promoters hawking "free" goods or using obscure terminology to hide the dangers or costs associated with their products.
It's true that one major air cleaner marketing scam is selling the filtered air purifier cheap as a loss leader for high priced replacement filters.
But just as common is the "costless" siren song about never buying replacement filters.
The notion of an effortless air purifier appeals to me greatly.
That's why I like my Sharp Plasmacluster: automatic operation and air filter replacement intervals up to 5 years.
While that is very close to the lowest possible cost of air purification, and is extremely low maintenance, it isn't filterless.
While I recommend true-HEPA filtered air purifying devices, to establish a base level of purified air, here is a review of air purification technologies without air filtration.
Filterless Purifier Options
The majority of aircleaners sold as not needing replacement air filter media are electronic: electrostatic precipitators.
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 a pollutant source.
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" (for indoor medical devices, not air purifiers).
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 negatively charged 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.
But like any oxidizer, PCO can create partially-oxidized byproducts when the load factor is too high.
Sources must be removed before air cleaners are installed.
Ionizers using both polarities, positive and negative, to charge the airflow, can create an oxidation technology which floats on water molecules in the air, destroying particles and inactivating microorganisms.
But this technology is also generally combined with filtration or ozone.
HEPA filtering air purifier technology is the base, the standard by which emerging filterless air cleaner concepts are measured.
No flawless filter-free air purifier has been developed, most have risks or defects.
I encourage everyone to try the PCO and Plasmacluster technologies, but not to be fooled by pie in the sky marketing.