(1) (Comb; Fire Pr) a. To be on fire. To be consumed by a rapid, flaming or incandescent oxidation process that produces heat. b. Damage or injury caused by heat. (2) (First Aid; Med) a. Injury by heat, electricity, chemicals, friction, irradiation, or cther cause resulting in the destruction of skin and underlying tissues in varying degree. b. A prickling or itching sensation. c. The mark or trace left on the skin by a burn injury. See: Scald; Skin. Note: Burns Are Classified As First Degree, Redness of the skin; second degree, blisters and some broken skin; and third degree, with char-ring and full thickness skin destruction. Third-degree burns, in contrast to first- and second-degree burns, are not painful, the nerve endings having been killed. Serious burns damage capillary walls, resulting in loss of circulation of blood plasma, and edema (fluid infiltration) in the damaged areas. Skin will blister (second-degree burn) at a temperature of 160°F. A temperature of 250°F can be tolerated with great discomfort for 15 minutes, depending on dryness of the air. At 300°F irreversible damage is done to the skin in one minute. It is reported that dry air up to 300°F can be breathed for a short time, but not moist air, which causes extensive deep lung damage