Do not panic and close the hopper and cooking chamber lid to cut off the fire’s oxygen supply. Unplug the grill and let cooking temperatures come down gradually. Wait for the fire to die down. You may want to put water into the Traeger grill to cool it down, but this would only increase the Traeger smoke coming out of the pellet box. Traeger grill is an electrical equipment, and it's never safe to put water into such a machine.