First-degree, second-degree, third-degree and fourth-degree burns differ mainly in the depth of tissue damage, appearance, pain, healing time and the medical care required. Understanding these differences is important in fire safety because the severity of burns determines the urgency and type of emergency response. First-degree burns are the mildest form and affect only the epidermis, the outermost layer of the skin. They commonly result from brief exposure to flames, hot surfaces, steam or sunlight. The affected area becomes red, dry and painful, but blisters are generally absent. A typical example is mild sunburn. These burns usually heal within a few days to about a week without permanent scarring. Immediate cooling with cool running water can help reduce pain and further tissue damage. Second-degree burns are more serious because they extend through the epidermis and into part of the dermis. They are often caused by direct contact with flames, hot liquids, steam or heated objects. The skin may appear red, swollen, moist and blistered, and the affected area is usually very painful because nerve endings remain partly