During a fire, that level, decreases rapidly. When it drops below 17 percent, people breathing the air will experience decreased muscle control and decreased thinking ability. They may become uncoordinated, making escape more difficult. When the oxygen level drops below 11 percent, breathing stops. After four to six minutes without oxygen, brain death occurs.
Fires produce smoke and poisonous gases.
These are the leading causes of death in house fires. Most house fires occur at night while people are sleeping. A sleeping person may not wake up or collapse when they awaken. A fire can produce intense heat, which can exceed 1000 degrees. Breathing smoke and superheated air can cause lung damage.