Filtration

The most important step in filtering your air is also the simplest: Replace your furnace filter every three months if you have a forced-air system. The American Lung Association says that 3M's Filtrete brand filters are particularly effective at removing particles. They come in various levels, depending on how fine the particles are that they trap. If you suffer from allergies, spend the $15 on the finest filter. Buy three or four when they're on sale, then mark your calendar to replace them every three months.

Weekly vacuuming also filters the air. If you have allergies, consider vacuuming carpeted areas more frequently. There's been a lot of hype recently concerning high efficiency particulate air (HEPA) filters. Vacuum cleaners with HEPA filters are effective at capturing fine particles that can trigger allergic reactions, but don't scrap your old vacuum cleaner yet. If it has a hard, solid casing around the bag and some kind of filter in the exhaust, it's probably doing a fine job. You can upgrade any vacuum cleaner's filtering power by buying filtered bags, which are now made to fit most standard vacuum cleaners. And don't stop at the floors. Use an attachment to vacuum upholstered furniture, which accumulates dust and air impurities.

Should you spend the money on a room air purifier? One with a HEPA filter? A deionizer? According to Dr. Cugell, all these devices are overrated. "There should be little need for HEPA filters, unless there's severe breathing difficulty. Room filters are expensive and not especially effective. There's rarely a need for that type of purification."