To understand if succulents purify air, we must first examine the fundamental physiological processes of plants. All plants, including succulents, engage in photosynthesis and respiration. During the day, photosynthesis dominates: plants absorb carbon dioxide (CO2) and release oxygen (O2). At night, respiration takes over: plants absorb oxygen and release carbon dioxide, just like animals. This continuous gas exchange is a basic form of "air purification," as it alters the composition of the surrounding air. However, the primary goal of this process is energy production for the plant's survival, not the targeted removal of human-made pollutants. Therefore, while they do contribute oxygen, this is a general function of their metabolism rather than a specialized purification act.
The popular belief that houseplants purify air largely stems from a famous NASA study conducted in the late 1980s. The research aimed to find ways to purify air in sealed spacecraft environments and concluded that certain plants could remove volatile organic compounds (VOCs) like benzene, formaldehyde, and trichloroethylene from the air. It is crucial to note that the study tested a variety of tropical plants, such as peace lilies and spider plants, which have high transpiration rates (the process of water movement through a plant and its evaporation from leaves). This high transpiration rate pulls air down to the root zone where microbes in the soil break down the VOCs. Most succulents, having evolved in arid environments, are masters of water conservation. They exhibit very low transpiration rates to prevent water loss. Consequently, their mechanism for moving air through the soil is significantly less effective than that of tropical foliage plants.
Succulents possess a unique metabolic adaptation called Crassulacean Acid Metabolism (CAM). To minimize water loss in hot, dry climates, CAM plants keep their stomata (pores on the leaf surface) closed during the day and open them at night to take in CO2. This is the opposite of most plants. This leads to a key differentiator: many succulents continue to release oxygen at night because they are still processing the CO2 absorbed during the previous night. From a human perspective, this makes them desirable bedroom plants, as they can slightly increase oxygen levels while you sleep. However, this nocturnal oxygen release is still part of the basic gas exchange process and is not directly linked to the removal of harmful VOCs. The CAM pathway does not inherently make a plant a more potent air purifier; it simply shifts its metabolic timetable.
From a purely botanical perspective, the air-purifying capability of any single houseplant is relatively modest. The NASA study's results were achieved in a small, sealed chamber with a high density of plants. To achieve a similar effect in a standard-sized room, one would need a very large number of plants—estimates often range from 10 to 100 per square meter. Given that most succulents are slow-growing and have low transpiration rates, their individual impact on indoor air quality is minimal compared to faster-growing, leafy tropical species. Their primary contribution is the general benefit of adding a living organism to your space, which can slightly increase humidity and oxygen levels, but this falls far short of being a significant air filtration system.
