The Chlorophytum comosum, commonly known as the spider plant, is a popular houseplant valued for its cascading foliage and ease of care. It has long been championed as a natural solution for improving indoor air quality, a belief that has driven its popularity in homes and offices. The premise is that plants can actively filter the air, removing harmful chemical contaminants that accumulate indoors. This article investigates the scientific basis for this claim, examining the research and assessing its practical relevance in a typical home setting.
The Research That Started the Claim
The concept that houseplants purify indoor air originates primarily from the 1989 NASA Clean Air Study, spearheaded by Dr. B.C. Wolverton. This initial research focused on developing a biological life-support system for closed environments, such as sealed spacecraft, requiring a low-energy method to regenerate air and remove toxic byproducts. The NASA study involved placing individual potted plants inside small, sealed plexiglass chambers, typically around 0.9 cubic meters in volume. High concentrations of specific airborne chemicals were injected into these enclosures, far exceeding levels found in a normal building. Monitoring the air over a short period (24 to 72 hours) established the plant’s capacity to remove toxins under extremely controlled, non-ventilated conditions.
Specific Airborne Pollutants Targeted
The NASA research concentrated on removing specific Volatile Organic Compounds (VOCs) routinely found in modern indoor environments. These compounds are released by synthetic materials and common household products, contributing to “Sick Building Syndrome.” Spider plants demonstrated an ability to remove substances like formaldehyde, benzene, and trichloroethylene (TCE). Formaldehyde is a common indoor air pollutant, off-gassing from materials such as pressed-wood furniture, carpeting, and cleaning products. The ability of the plant-soil system to process these chemicals in a sealed environment confirmed a biological mechanism for phytoremediation.
How Plants Filter Indoor Air
The process by which plants and their associated systems remove gaseous pollutants is a two-pronged biological mechanism known as phytoremediation. The first part involves the plant’s leaves, which absorb airborne chemical molecules through the stomata. These are small pores on the leaf surface primarily used for the exchange of carbon dioxide and oxygen during photosynthesis. Once inside the plant, some of these absorbed VOCs are metabolized by plant enzymes and converted into harmless compounds, with some being stored within the plant tissues.
The Role of Soil Microbes
The most significant component of this air filtration system is the root structure and the surrounding soil. This area, known as the rhizosphere, hosts a dense community of beneficial microorganisms. These soil microbes are responsible for the majority of the detoxification process. As the plant transpires, it draws air down toward the roots, exposing the pollutants to the microbial community. The microorganisms then break down the complex organic chemical compounds, using them as a source of energy and carbon.
Translating Lab Results to the Home Environment
While laboratory findings established the spider plant’s biological capability to process VOCs, translating those results to a real-world home environment requires a significant adjustment in perspective. The controlled conditions of the NASA study—a small, sealed chamber with high pollutant concentrations—do not accurately reflect the dynamic conditions of a typical house or apartment. Unlike a sealed plexiglass box, real homes have constant air exchange with the outside, known as the air exchange rate (AER).
Practical Limitations
Normal ventilation in a building, even a relatively well-sealed one, dilutes and replaces indoor air much faster than a few potted plants can clean it. Subsequent research examining plant efficacy in real-world settings with natural airflow found that the impact of plants on overall air quality is minimal to negligible. The rate at which outdoor air enters the home is the dominant factor in pollutant removal. To achieve an air-cleaning effect comparable to standard mechanical ventilation, the necessary number of spider plants would be impractical for most homes. Studies have calculated that to match the air purification rate of a typical ventilation system, a homeowner would need between 10 and 100 plants per 100 square feet of floor space.