An HVAC decontamination system with regulated ozone output based on monitored ozone level in ambient air is disclosed. The HVAC decontamination system includes an ozone supply unit and an air analyzer. Based on one or more control signals from the air analyzer, the ozone supply unit is configured to: (i) generate ozone when an amount of ozone per unit volume of air is less than a predetermined threshold; and (ii) cease to generate ozone when the amount of ozone per unit volume of air exceeds the predetermined threshold.