House plants improve indoor air quality because they take in carbon dioxide and expel oxygen. Human beings inhale oxygen and expel carbon dioxide. Thus, house plants can lower the levels of carbon dioxide and increase the levels of oxygen in the home, both of which benefit their human hosts.
Photosynthesis is a set of chemical interactions by which plants take in sunlight and carbon dioxide through their leaves and water through their roots, and use these components to manufacture food. Each carbon dioxide molecule contains one atom of the element carbon and two atoms of the element oxygen. Each water molecule contains two atoms of the element hydrogen and one of oxygen.
During photosynthesis, plants use the energy from sunlight to split carbon dioxide molecules and water molecules down into their component atomic parts. Then they resemble the atoms into carbohydrates for food.
Byproducts, Plant and Human
Finally, plants "exhale" the extra oxygen (O2) left over from the chemical reactions back out into the atmosphere. Human beings, on the other hand, inhale air to take in oxygen, which is vital to the process of turning food into energy. They then exhale carbon dioxide back into the atmosphere as a byproduct.
Beyond CO2 and O2
Besides this elemental, and symbiotic, exchange, some plants also remove other toxic gases from the air in homes. Organic Jar.com reports that in research aimed at finding ways to clean air in self-contained space crafts, scientists at NASA have studied many different house plants to see which ones were most effective at "scrubbing" the air. They learned that in addition to consuming carbon dioxide and releasing oxygen, some of the most commonly grown house plants also remove toxic chemicals such as benzene, formaldehyde and trichloroethylene from the air. Many common construction materials used to build houses contain these chemicals, which slowly vaporize into the atmosphere of the house over time.
The Best Air-Scrubbers
NASA has determined that the 15 best house plants for purifying indoor air, from the most effective to the least, are Oxycardium philodendron (also called heartleaf philodendron or Philodendron scandens); Philodendron domesticum (elephant ear philodendron); Massangeana (cornstalk dracaena or Dracaena fragrans); Hedera helix (English ivy); Chlorophytum comosum (spider plant); Janet Craig dracaena (Janet Craig or Dracaena deremensis); Warneck dracaena (Warneckii or Dracaena deremensis); Ficus benjamina (weeping fig); Epipiremnum aureum (golden pothos); Mauna loa (peace lily or Spathiphyllum); Philodendron selloum (Selloum philodendron); Aglaonema modestum (Chinese evergreen); Chamaedorea sefritzii (bamboo or reed palm); Sansevieria trifasciata (snake plant); and Dracaena marginata (red-edged dracaena).