The Snake Plant, or Mother-in-Law's Tongue, is one of the most recommended plants for improving air quality. The optimal place to keep this relatively inexpensive and low-maintenance plant is the bedroom, because it converts CO2 into oxygen at night.

Keep a Snake Plant in Your Bedroom to Improve the Air Quality While You Sleep

In its roundup of the best cheap plants for improving indoor air quality, Wisebread notes that Mother-in-Law's Tongue is recommended by a NASA study (which lists at least a dozen air-improving plants) and researcher Kamal Meattle, who has shown us that just three common houseplants can improve indoor air.

Meattle says Mother-in-Law's Tongue is known as "the bedroom plant." While most plants take away oxygen at night, this one gives off oxygen at night. The plant also filters formaldehyde, trichloroethylene, xylene, toluene, and benzene from the air. Meattle recommends 6-8 waist-high plants per person for optimal output from this oxygen factory.