A method of exterminating organisms is provided utilizing heated circulating air. First, a determination is made as to which enclosed areas of the building or other structure are to undergo extermination. This step defines an application zone. Next, a desired elevated 
temperature limit is established for heated air that is to be circulated through the application zone. Heaters are provided in 
airflow communication with the application zone, and circulation fans are positioned throughout the application zone to move the heated air for proper 
heat distribution. The heaters utilize an amount of recirculated air already present in the application zone to 
cut down on the amount of energy needed to raise the 
air temperature within the application zone towards the desired elevated 
temperature limit, and to eliminate the need for high CFM 
airflow heaters to achieve 
air temperature elevation. The temperature at various nodes within the application zone may be monitored to allow personnel to redirect circulating 
airflow within the application zone to balance out areas of higher 
air temperature with areas of lower air temperature. The method takes 
advantage of 
convection heat transfer to raise the temperature evenly within an application zone, minimizing 
temperature stratification which could result in ineffective pest extermination and / or damage to equipment and facilities.