Fire Basics

All fires require oxygen, fuel and heat.  These three elements brought together in the right combination will produce fire and are known collectively as the "fire triangle."

To better understand how fires work, modern fire experts have expanded the "fire triangle" to include a fourth element.  The fourth element is the complex molecular chain reaction between the fuel and the oxygen that keep a fire burning once it has started.  The resulting diagram is called the "fire tetrahedron."

Oxygen is all around us and almost any material can become fuel for a fire:  clothing, furniture, wood, paper, plastics, flammable gases and flammable liquids such as gasoline.  All it takes is a human act or oversight, a mechanical or electrical malfunction, or some natural event such as lightning to bring oxygen fuel and heat together to create a fire.

Fires can be extinguished by removing just one of the elements of the "fire tetrahedron."  Removing the fuel, cutting off the supply of oxygen, reducing the fuel's temperature, or disrupting the chemical chain reaction will extinguish the fire.

How Fires Kill

Severe burns are only one cause of fire deaths. Only about one-fourth of home fire victims die from burns. The majority die from inhaling poisonous gases found in the smoke or from lack of oxygen.

Once a fire starts, its effects on the atmosphere can quickly make your home a deadly place. Fire consumes oxygen. Normally, the air we breathe is 21 percent oxygen. During a fire, that level drops rapidly. If it drops below 17 percent, people breathing the air will have difficulty thinking clearly and controlling their muscles. They may become irrational and uncoordinated, making escape more difficult. When the oxygen in the air drops into the 10 to 12 percent range, four to six minutes without oxygen will cause brain death.

Smoke inhalation is the leading cause of death in fires. Fires produce smoke that contains poisonous gases that can kill you long before the flames reach you. The majority of fatal home fires happen at night when people are asleep. A sleeping person who inhales poisonous gases may never wake up, or may pass out as soon as he or she stands up to escape.

There are four common deadly gases associated with fires in the home. These gases are carbon monoxide, hydrogen cyanide, hydrogen chloride and carbon dioxide.

• Carbon monoxide is a poisonous gas that displaces oxygen in the blood. It is the most abundant of all fire gases and is produced by all fires.
• Hydrogen cyanide is also a deadly poison produced by burning wool, silk, nylon and some plastics. Common elements in blankets, upholstered furniture, curtains and clothing.
• Hydrogen chloride irritates your throat and eyes, increasing your breathing rate and making it difficult to see to escape. The increased breathing rate causes you to inhale all the toxic byproducts of fire faster.
• Carbon dioxide in the air causes you to breathe faster, increasing you intake of the other poisonous gases released by fire.

Smoke also contains particles of burned fuel that obscure light. The particles decrease visibility and irritate your eyes causing a further decrease in visibility.

Fires produce intense heat, sometimes in excess of 1100 degrees. Intense heat will burn exposed skin and damage your body through heat stress. Breathing superheated air can also cause rapid and severe lung damage. None of the human body’s natural temperature regulating mechanisms such as breathing and perspiring can keep pace with the heat and exposure to such extreme temperatures can cause unconsciousness in seconds.

Surviving a Home Fire

To survive a home fire, you must be prepared and respond quickly. You need to have fire protection systems such as smoke alarms and automatic fire sprinkler systems that can detect and or control a fire quickly. You need to know what to do. In a fire emergency, seconds count.