According to the U.S. Environmental Protection Agency, Americans spend 90% of their time indoors, where indoor air is two to five times more polluted than outdoor air. Toxins in the built environment have been found to cause adverse physical and mental health effects on occupants and are estimated to cost the United States $125 billion annually in lost productivity. To address this challenge, a novel botanical air filter was developed for improving indoor air quality (IAQ) in buildings. The "biowall"is envisioned as an integral part of the heating and cooling system for ahomeor smallcommercial building, where it will remove airborne contaminants by leveraging the natural ability of plants to metabolize harmful volatile organic compounds (VOCs). This research evaluated a prototype biowall in an environmental chamber where temperature, relative humidity, and toxin levels were precisely monitored. A known amount of contaminant was introduced into the chamber and then its decay was monitored both with and without the botanical air filter. The results showed that the biowall reducedVOClevels by 60% without having an adverse effect on the relative humidity of the occupied space. These data were used to develop and calibrate a thermodynamic model of the biowall. In the long term, this research could lead to the broader use of performance-based standards for IAQ that save energy by reducing the amount of outdoor ventilation air used for maintaining high levels of IAQ.