What is the main catalyst for plant air purification?

Air must contact the plant roots.

Wolverton determined that:

The studies showed that 50 to 65 percent of VOC removal is attributed to root and soil microbes.

Studies show that both the plant leaves and root microbes contribute to the removal of VOCs from the indoor environment. It has been well documented that plant leaves can absorb, metabolize and/or translocate certain VOCs to the root microbes where they are broken down. Studies show that 90 percent of these substances are converted into sugars, new plant material and oxygen. Scientists at the GSF-National Research Center for Environment and Health in Neuherberg, Germany produced the most definitive study yet on this phenomenon. They used radioactive carbon tracers to follow how the spider plant (Chlorophytum comosum L.) was able to breakdown and destroy formaldehyde.

Plants also employ another mechanism to move air down to their root system. Plants transpire (emit water vapor from their leaves) by moving water up from their roots to their leaves. In the process, a small convection current is created pulling air down to the root zone. Through the transpiration process, a plant not only moves atmospheric gases such as oxygen and nitrogen to its root zone, but also any airborne chemicals present. Because of this action, generally a plant with a high transpiration rate is more effective in its VOC removal capacity.

Wolverton determined that the more the roots were exposed for receipt of the gases, the more efficiently the plant could remove the toxins from the air.

Cleck next page for the next 3 pages to see 3 ways air gets to the roots of the plant air filter.