Air purifiers are designed to filter fine particulates out of the air in a room. This can be helpful for those suffering from asthma or allergies, and can also help reduce the amount of tobacco smoke in the air.
There are a number of types of filtration available. The most common classification are known as High Efficiency Particulate Air (HEPA) filters. These air purifiers are good at catching pollen, mold spores, and dust, but require periodic filter changing.
So-called Charged Media Filters filter air using static electricity, enabling them to collect extremely fine particles. But these, too, require frequent filter changing.
Electrostatic Precipitators are another class. These use an electric charge to trap particles on a collector plate. The big advantage here is that you can take the plates out and wash them, so you’ll never need to buy new filters.
Factors to bear in mind when buying include how noisy the device is, how often you’ll need to replace the air purifier’s filters (and how much they’ll cost each time), and what size of room the unit is designed for. Also bear energy efficiency in mind, since air purifiers will often run continuously for long periods of time. The lower settings will typically draw about 50 watts, or roughly the same as an incandescent light bulb. At the very least, buy a device with Energy Star certification.