Succulents are desert-adapted plants with thick, fleshy parts designed to store water, making them popular houseplants. People often seek them out for the promise of cleaning indoor air. Succulents do filter air, but their method is fundamentally different from most common houseplants, relating directly to how they manage gas exchange to survive in arid climates. Indoor air often contains Volatile Organic Compounds (VOCs), which are gases released from materials like paint, furniture, and cleaning supplies.
How Plants Filter Indoor Air
The process by which plants clean the air is known as phytoremediation, involving both the leaves and the soil. Most common indoor plants, classified as C3 plants, open tiny pores on their leaves called stomata during the day. This opening allows the plant to take in carbon dioxide for photosynthesis and provides a pathway for airborne pollutants, such as formaldehyde, to enter the leaf structure.
Once absorbed, the plant’s metabolic processes break down some volatile organic compounds into less harmful substances. However, the plant is only one part of the air-cleaning system. The soil surrounding the roots contains a dense community of microorganisms, including bacteria and fungi, which play a larger role in pollutant removal.
As the plant transpires, it draws air down toward the root zone, where these soil microbes consume the airborne toxins. These microorganisms metabolize the pollutants, converting them into nutrients, carbon dioxide, and water. For C3 plants, this absorption and breakdown cycle is active during the sunlit hours when their stomata are open.
The Unique Function of Succulents
Succulents, including popular varieties like the snake plant, utilize a specialized form of photosynthesis called Crassulacean Acid Metabolism (CAM). This metabolic pathway is a desert adaptation that allows the plant to conserve moisture by altering its gas exchange schedule. Unlike C3 plants, CAM plants keep their stomata tightly closed throughout the hot, sunny hours.
Succulents open their pores only at night when temperatures are cooler and humidity levels are higher, reducing water loss. During the night, the plant takes in carbon dioxide and converts it into malic acid, which is stored until daylight. When the sun rises, the stomata close, and the stored malic acid is broken down to release carbon dioxide internally for photosynthesis.
This nighttime gas exchange has a direct implication for indoor air quality, as the plants actively absorb air from the room when the house is typically sealed. Air pollutants are absorbed through the stomata alongside the carbon dioxide during this dark phase. Because succulents absorb air and release oxygen primarily at night, they are unique contributors to a home’s air quality, especially in bedrooms.
Practical Effectiveness in Home Environments
The foundational research on houseplants and air filtration stems from the 1989 NASA Clean Air Study, which demonstrated that plants could remove VOCs from the air. These experiments were conducted in small, sealed laboratory chambers with pollutant concentrations much higher than those found in a typical home. The controlled conditions maximized the plants’ pollutant removal rate without considering real-world airflow dynamics.
Current research emphasizes that the air-cleaning capacity observed in these studies does not translate directly to a standard residential setting. The Air Exchange Rate (AER) of a home—the rate at which indoor air is replaced by outdoor air—is the dominant factor in pollutant removal. Even a home with minimal ventilation typically has an AER that far exceeds the purification rate of a few houseplants.
To match the air filtration of an average home’s mechanical ventilation or opening a window, an impractical density of plants would be required. Estimates suggest that achieving a measurable reduction in VOCs requires placing between 10 and 100 plants per square meter of floor space. While succulents technically filter air, the practical effect of a small collection on overall indoor air quality remains negligible compared to basic ventilation.