Home should be a sanctuary, but according to the Environmental Protection Agency, the air within most houses (and office buildings) can be more polluted than the air outside in even the largest, most industrialized cities. The culprit: volatile organic compounds like formaldehyde, which are offgassed from plastics, upholstery, furniture, and other synthetic (and so-called “natural”!) materials. While it’s nearly impossible to prevent this indoor air pollution, there is a low-tech purification fix: houseplants. “Plants are as efficient at filtering air as some of the most high-tech machines,” says Renée Loux, green-living expert and author of Easy Green Living. “Plus, they’re beautiful and add moisture to the air.” Here, Loux’s advice on finding the right plant for you.