The New York Times, as well as Newsweek, carry ads for the Venta-Airwasher that claims it's both a humidifier and a purifier.

Consumer Reports' Rico De Paz just checked out two sizes. One costs $200 dollars, the other is $400.

The devices claim they can trap "even the very finest particles, as small as 10 microns."

"Many of the particles that bother people with respiratory problems like dust and smoke are a lot smaller. Particles that are 10 microns are just too heavy to stay suspended for very long," says De Paz.

Consumer Reports tested the Venta-Airwasher the same way it tests all air purifiers, in a sealed chamber. A measured amount of fine dust is put into the room followed by cigarette smoke.

A particle counter keeps track of the number of particles in the air that are three microns or smaller.

"The Venta-Airwasher didn't do anything to clean the air of very small particles. This is smoke and this is dust. You can see that the number of particles stayed the same over the course of 90 minutes," says De Paz.

So tests show it's not a good air purifier. How about as a humidifier? The tests show the Venta-Airwasher does add moisture, but it doesn't have a control to let you set the level of humidity.

"Without humidity controls, the air can get very moist, and eventually cause mold and mildew to grow," De Paz says.

A regular humidifier costs a lot less. Consumer Reports says get one with a control that lets you set the amount of humidity you want.

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