 Above the auger is a heat shield to disperse the direct heat before it reaches the heat box to allow the wood smoke to keep the heat box at an even temperature throughout.The heat sensor inside the heat box relays the current temperature inside the box back to the temperature regulator which then controls the fan speed and pellet hopper motor which will either increase or decrease the amount of pellets in the auger or the amount of air available to the fire to maintain the desired temperature for the cook.The popularity of this type of smokers is on the rise after many BBQ pit-masters started using them for competition barbeque.