Succulents, with their striking forms and low-maintenance requirements, have become some of the most popular indoor plants. Their ability to thrive on minimal water makes them an attractive option for homeowners seeking to add some greenery to their living spaces. The belief that succulents actively purify indoor air has become widespread, often influencing purchasing decisions. Does the science support the claim that these hardy plants significantly improve the air quality inside a home? To understand the specific role of succulents, it is necessary to examine the general biological process by which all houseplants interact with atmospheric pollutants.
The Science of Plant Air Purification
All plants engage in a process known as phytoremediation, which is the overall method of using living organisms to remove contaminants from soil, water, or air. The initial intake of gaseous pollutants occurs through tiny pores on the leaves called stomata, which primarily serve for the exchange of carbon dioxide (CO2) and oxygen (O2). These pores also allow the absorption of Volatile Organic Compounds (VOCs), which are harmful chemicals emitted from common household items like paints, furniture, and cleaning products. Specific VOCs like formaldehyde, benzene, and trichloroethylene can enter the plant tissue through these leaf openings.
While the leaves absorb some pollutants, the most significant component of air purification is concentrated in the root zone. Once absorbed by the plant, many VOCs are translocated down to the roots. The soil and potting mix contain billions of microorganisms, including bacteria and fungi, which exist in a symbiotic relationship with the plant. These soil microbes break down the VOC molecules into simpler, non-toxic substances, converting the pollutants into products like water, carbon dioxide, and biomass. The health and activity of this microbial community within the rhizosphere—the area immediately surrounding the roots—are directly related to the plant’s air-cleaning capacity.
The Succulent Advantage: CAM Photosynthesis
The biological mechanism that separates many succulents from other houseplants is Crassulacean Acid Metabolism, or CAM photosynthesis. Most plants, called C3 plants, keep their stomata open during the day when sunlight is available for photosynthesis, which results in significant water loss through transpiration. Because succulents are adapted to arid environments, they have evolved a strategy to conserve water.
CAM plants, such as Snake Plants and Jade Plants, operate on a reversed schedule. They open their stomata exclusively at night when temperatures are cooler and humidity is higher, significantly reducing water loss. During this nocturnal period, they absorb CO2 from the air and store it internally as malic acid. The stored malic acid is then converted back into CO2 during the day while the stomata are closed. This daytime release of CO2 fuels the plant’s photosynthesis without the need to open its pores and lose water. This nocturnal gas exchange is the origin of the common belief that succulents are uniquely beneficial for bedrooms, as they continue to process air overnight when many other plants are metabolically less active.
Practical Effectiveness and Limitations
The claims about houseplants purifying indoor air stem from the 1989 NASA Clean Air Study. This research demonstrated that common houseplants could remove VOCs like benzene and formaldehyde from the air. However, the experimental conditions of the NASA study were controlled and involved placing individual potted plants inside small, sealed plexiglass chambers.
This sealed environment is fundamentally different from a typical, large, and ventilated home or office building. In real-world settings, ventilation systems constantly introduce fresh air from outside, which dilutes VOCs at a rate that far exceeds the capability of a few potted plants. The high pollutant concentrations used in the sealed chamber studies are also rarely found in residential spaces.
While plants possess the biological machinery to absorb and neutralize airborne toxins, their practical impact on air quality in a standard room is minimal. To achieve a measurable reduction in VOCs comparable to mechanical air filtration, research suggests a high density of plants would be necessary. For instance, studies estimate that it would require between 10 and 1,000 plants per square meter of floor space to match the air exchange rate provided by typical ventilation. For the average homeowner, a few succulents will not replace an air purification unit or proper ventilation. Their primary benefit remains their positive effect on well-being and the aesthetic improvement of a space.