Firefighters have one of the most hazardous of all occupations. It is also one of the most essential for nothing is more damaging or more deadly than fire. Swinging a fire axe or aiming a fire hose that shoots water at 300 pounds per square inch requires strength and stamina. But firefighting isn't only about being physically fit. Most calls to fire departments involve medical emergencies, and many fire departments require firefighters to be certified as emergency medical technicians in order to provide on-site care to victims of accidents, natural disasters or crimes. More than 90 percent of all career firefighters work in city or county fire departments. But firefighters are also employed by airports, chemical and manufacturing plants, and by agencies responsible for fighting forest fires. Opportunities may also be available in volunteer fire departments, though these may be limited because the increased level of specialized training needed makes it more difficult for volunteers to remain qualified. Firefighters also aid victims of earthquakes, tornadoes and other natural disasters. They may help clean up oil spills and hazardous materials, and many firefighters are involved in public education and fire prevention activities. Since the best fire is the one that never gets started in the first place.