An air purification system for a heating, ventilation, and air conditioning (HVAC) system includes an ozone generating device that is used to introduce ozone into an air stream flowing through the ozone generating device. The ozone is used to remove contaminants, including volatile organic compounds (VOCs), from the air stream. The purification system includes sensors in various locations within the HVAC system to measure a concentration of constituents in the air. In some embodiments, the constituents may include ozone and VOCs, such as toluene, butene, and propanal. To control an amount of ozone generated, the purification system controls an amount of electrical power to the ozone generating device. To control a concentration of ozone generated, the purification system controls a flow rate of air through the ozone generating device.