Air Filtration

The single-most important characteristic by which to assess filtration efficiency is it's efficiency at capturing very small particles and microbes.

Generally, airborne pathogens increase in size from viruses (0.01 to 0.3 microns) to bacteria (0.2 microns) to fungi (1 to 20 microns). A micron (short for micrometer) is one-millionth of a meter. It can also be expressed as one 25-thousandth of an inch

Based on ASHRAE's new Minimum Efficiency Reporting Value (MERV) rating system for air filters in Standard 52.2-1000, "Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size":

• Mechanical arrestance of fungi (spores) requires filters with MERVs of 9 to 12 (with up to 90% efficiency in the 3 to 10 micron range).
• Mechanical arrestance of bacteria requires filters with MERVs of 13 to 16 (with up to 95% efficiency in the 0.3 to 1.0 micron range).
• Mechanical arrestance of high percentages of viruses requires high efficiency particulate arrestance (HEPA) filtration, beyond the range and outside the scope of the ASHRAE MERV rating tests.

Air Cleaners Tested

Performance varies widely
 

Sales of portable air cleaners have skyrocketed. Americans bought nearly 3.5-million last year.

Sharper Image dominates the market, in large part due to the brisk sales of its ionic breeze line. Now, the company's success has encouraged others to come out with imitators.

A five-minute infomercial for the Ionic Breeze Quadra promises to clean room air with what it calls its "exclusive technology."

Consumer Reports just evaluated the Quadra along with 17 other portable cleaners. The tests were performed in a sealed chamber.

To evaluate how quickly the machines can remove tiny particles from the air, testers use fine dust and cigarette smoke; substances used in standard industry tests. Air cleaners that do a good job removing these should be effective on a wide range of particles.

In one test, a small, measured amount of smoke is injected into the room and a machine counts the number of particles in the air as well as measuring the size of those particles.

Consumer Reports' David Pittle says many portable cleaners have no trouble clearing the air quickly.

Pittle says, "The Friedrich air cleaner that we tested cleared the air at a very rapid rate. It reduced the pollution levels in the room to nearly zero within a half hour."

But it was a different story with the Ionic Breeze Quadra.

"In the same test, the Ionic Breeze Quadra had a very slow rate of cleaning," Pittle said. "And when we tested it over a longer period of time, its cleaning performance did not improve."

Tests show two other room cleaners that work like the ionic breeze, the Honeywell Environizer and the Hoover Silentair 4000, also rated poorly in cleaning performance.

Pittle says, "It's important to emphasize that our tests are conducted in a sealed test chamber. In a home environment normal air exchange creates a constant influx of pollutants. Our tests show, and independent experts confirm, that these air cleaners don't work fast enough to be effective."

For that reason, Consumer Reports says the Ionic Breeze Quadra, Honeywell Environizer, and the Hoover Silentair 4000 are not worth buying.

If you are still interested, Consumer Reports recommends the following air cleaners:

• Friedrich, model C-90a for $500
• Whirlpool, model AP45030h0 for $270