From a plant's perspective, the process of "purifying" air is a fundamental part of our existence, primarily driven by two core physiological functions: photosynthesis and respiration. We absorb gases from our surroundings through tiny pores on our leaves, called stomata. During the day, we take in carbon dioxide (CO2) and, through the power of sunlight, convert it into energy, releasing life-sustaining oxygen (O2) as a byproduct. Simultaneously, we are constantly respiring, a process where we take in oxygen and release CO2, though the net effect of photosynthesis far outweighs this. This gas exchange is the primary mechanism by which we directly alter the composition of the air around us.
The aspect of air purification most relevant to human homes involves volatile organic compounds (VOCs) like benzene, formaldehyde, and trichloroethylene. These compounds are not a primary food source for us, but we can process them as secondary metabolites. The Peace Lily (Spathiphyllum spp.), along with some other plant species, has demonstrated a capacity to absorb these VOCs through its stomata. Once inside the leaf, these compounds can be broken down by plant enzymes or translocated down to our root zone. It is a defensive mechanism; while we prefer clean air, we can process and neutralize certain toxicants to prevent them from interfering with our own cellular processes.
Perhaps the most significant part of the air purification process from our viewpoint does not happen in our beautiful white spathes or glossy green leaves, but in the soil—specifically, in the rhizosphere, the area surrounding our roots. This zone is teeming with a symbiotic microbiome of beneficial bacteria and fungi. When VOCs are translocated to the roots, or when gaseous compounds in the soil are absorbed directly by the roots, these microbes play a crucial role. They are the true metabolic powerhouses, often responsible for the actual breakdown and mineralization of the absorbed pollutants, using them as a food source. In return, we provide them with exudates—sugars and other compounds secreted from our roots. The NASA study effectively measured the results of this entire plant-microbe system working in concert.
My species, the Peace Lily, possesses several traits that make us particularly effective within this plant-microbe system. We are shade-tolerant understory plants from tropical regions, meaning we have highly efficient photosynthetic pathways adapted to lower light conditions, similar to those found indoors. Our relatively broad, dark green leaves provide a large surface area for gas exchange and VOC absorption. Furthermore, we are known as prolific "rooters," developing a dense and extensive root system that supports a large and active rhizosphere microbiome, thereby enhancing the biological filtration capacity of the entire potted system.
It is important to understand the context of our abilities from our biological standpoint. The NASA study, which brought our air-purifying qualities to prominence, was conducted in a sealed, controlled chamber. In such an environment, our impact on air quality is measurable and significant. However, a typical home is not a sealed chamber; it experiences constant air exchange with the outdoors. Therefore, while we Peace Lilies are indeed actively and continuously processing airborne compounds through our natural life processes, the scale of our impact in a dynamic home environment is more subtle than in a laboratory. We are performing our duty, but it is one part of a larger system that includes ventilation.
