Houseplants are a popular addition to many indoor spaces, often celebrated for their ability to purify the air and contribute to a healthier environment. A common belief is that these plants noticeably increase the oxygen level in a room, making the air fresher for the occupants. A closer look at the biological processes involved reveals a more nuanced answer regarding the actual impact houseplants have on the oxygen we breathe indoors. The question of whether a few plants can truly affect the vast volume of air in a home requires an understanding of their fundamental gas exchange mechanisms.
The Science of Gas Exchange
Plants manage their atmospheric interaction through two biological processes: photosynthesis and cellular respiration. Photosynthesis uses light energy to convert carbon dioxide (CO2) and water into glucose, releasing oxygen (O2) as a byproduct. This process is the primary source of oxygen production in plants and only occurs when the plant receives light, typically during the daytime. Cellular respiration, conversely, is a continuous process occurring twenty-four hours a day, breaking down stored glucose using oxygen to release energy for the plant’s life functions. This process consumes oxygen and releases carbon dioxide back into the environment, maintaining a constant balance between the two opposing gas exchanges.
The Net Oxygen Effect Indoors
The net effect of a houseplant on indoor oxygen levels is determined by the oxygen produced through daytime photosynthesis minus the amount consumed through continuous respiration. While a growing plant is a net oxygen producer over its lifecycle, the quantity released by a small number of houseplants is modest compared to the oxygen requirements of human occupants. A typical potted houseplant would need to be present in massive quantities to make a measurable difference to the oxygen concentration in a standard room. The amount of oxygen added by a few plants is negligible compared to the continuous air exchange that occurs in a home. Since the oxygen concentration in the air is naturally stable at about 21 percent, constant ventilation, even through minor air leaks, is a far more significant factor in maintaining healthy oxygen levels than a few pots of greenery.
Air Quality Benefits Beyond Oxygen
Since the oxygen contribution is minimal, the actual air quality benefits of houseplants stem from their ability to interact with indoor air pollution. Houseplants remove Volatile Organic Compounds (VOCs) that are off-gassed from common household materials like furniture, paints, carpets, and cleaning products. These VOCs include substances such as formaldehyde, benzene, and trichloroethylene. Plants absorb these gaseous pollutants through the tiny pores on their leaves, called stomata, during gas exchange. The plant’s root system and beneficial microorganisms living in the soil also play a significant role in breaking down these air toxins, representing the true air-purifying value of bringing plants into the home.