Fire fighting

by Chris Woodford. Last updated: May 16, 2011.

Fire gobbles its way through trees and buildings like a hungry animal—and in a sense that's exactly what it is: a living, breathing animal. Fire is a chemical reaction that feeds on fuel and oxygen. Give it plenty of both and it'll keep on burning indefinitely. Thank goodness, then, for firefighters, those brave men and women who set themselves the job of stopping fire in its tracks. Fire fighting is one of the toughest jobs there is and it calls for some equally tough equipment. Let's take a closer look at how to tackle those flames!

Photo: Firefighters wear all-over aluminum suits to tackle the worst blazes; suits made of fireproof Nomex® and Kevlar® are used for less severe fires. Photo by Nathan Lipscomb courtesy of US Navy and Defense Imagery.

Extraordinary people

Fire-fighting is a dangerous and demanding job that calls for total teamwork: it can take several people just to hold a powerful fire hose working at full pressure. Men and women make equally good firefighters, but must be no younger than 21 and usually retire at 55. Firefighters have to pass strict medicals and physicals and also take written theory tests. They're constantly trained in new fire-fighting techniques. Fire-fighting is a stressful job with long periods of waiting. Often firefighters pass the time at the station by playing games like table football.

Photo: Fire has a voracious appetite for oxygen and, when it burns materials such as plastics, it can give off highly toxic chemicals. That's why firefighters often have to wear breathing apparatus. Photo by courtesy of US Department of Energy (DOE).

Amazing equipment

What turns an ordinary man or woman into a firefighter? Apart from their sheer bravery and determination, it's the clothes they wear and the equipment they use. Firefighters wear jackets made from synthetic materials such as Nomex® and Kevlar®. They are fireproof, insulate against heat, and resist many different chemicals. Helmets, made from carbon-based composite materials, are hard-wearing and shockproof. A special mixture of glass and plastic protects visors against high temperatures.

Fire Engines

A fire engine has to carry firefighters and equipment to burning buildings. It also has to pump large volumes of water, sometimes over long distances, to extinguish the flames. Typical fire engines carry about 1900 liters (500 gallons) of water and draw bigger supplies from hydrants (like giant faucets positioned on streets—described more fully below) near the scene. They also carry assorted portable extinguishers for tackling smaller or more unusual fires.

Photo: A closeup of the pump inside an airport fire truck. You can connect several different hoses at once and each one has separate controls. There are stopcocks to turn the water on and off and dials to tell you the water pressure. Note the thick, insulated rubber boots the firefighter is wearing to to protect against heat, cold, and resist oils, chemicals, and salt. They also have steel toecaps to protect against impacts. Photo by Rebecca Layman courtesy of US Air Force and Defense Imagery.

Rescue Vehicles

Firefighters don't just put out fires. Most fire departments have dedicated rescue trucks designed for tackling automobile accidents, which carry hydraulic jacks and airbags for lifting overturned vehicles, a punch for breaking windscreens, and high-temperature gas torches that can cut people free from crashed cars. One new tool is a steering-wheel cover to stop a car's airbag from inflating and injuring firefighters as they work.

Fire ambulances

Ambulances are like miniature hospitals inside, allowing paramedics to give rapid treatment to casualties at the scene. firefighters tackle three quarters of all medical emergencies. Fire ambulances carry equipment to deal with common fire injuries. Respirators help people breathe normally after inhaling smoke. Special bandages and hydrocolloidal dressings provide treatment for burns. There are also masks, gloves, and overalls to isolate people contaminated by chemical spills.

Fire hydrants

A fire hydrant is really nothing more than a large outdoor faucet designed to supply huge amounts of water to fire engines, very quickly, whenever and wherever fires break out. A typical hydrant has up to four nozzles, one on each side, to which sturdy fire-hoses can be tightly screwed. To prevent tampering, the nozzles are held shut by pentagonal (five-sided) nuts that can be opened only with a special wrench. At the top, there is a similar nut and sometimes a wheel directly beneath it. Turning the nut and the wheel unscrews a valve inside the hydrant. This allows water to flow up from an underground pipe and out through whichever nozzles have been opened. Unlike an ordinary faucet, a fire hydrant is designed to operate either completely on or completely off.

Photo: Fire hydrants are like faucets that stop up water supplies under high pressure. That's why it sprays out when they're opened. Photo by Stephen Schester courtesy of US Air Force and Defense Imagery.

It can take an enormous amount of water, sprayed for several hours, to put out a large urban fire—and time is always of the essence for fire-fighters. Ordinary faucets could not possibly supply enough water to do this job quickly enough: they are designed to supply small amounts of water over short distances and at quite low pressures. In this respect, fire hydrants are very different. Where a domestic faucet can provide just enough water to power a garden hose around 2 cm (0.75 inch) thick, a fire hydrant can fill a hose up to eight times thicker. Even the most powerful domestic faucet can deliver only a few gallons of water every minute. But a typical fire hydrant can supply water up to a thousand times faster. The water from a fire hydrant is at several times higher pressure than the water in your faucets at home: it can come out of the hydrant at 80 psi or more (roughly six times the pressure of the air we breathe).

Tanked up

Fire hydrants are the most visible part of our emergency water systems—but they are not the only part. The water that supplies hydrants comes from large tanks or reservoirs usually located on hilltops. Each of these is designed to supply enough water to operate fire hydrants for hours at a time. The tanks are connected to the hydrants by a system of pipes laid out in a grid pattern. This means the water can travel from any tank to any hydrant via several different routes, so a hydrant will continue to work even if one of the pipes springs a leak. When a fire-fighter opens the valve on a hydrant, the force of gravity makes water run downhill from the tank, through the grid of pipes, to whichever hydrant nozzles are open. The higher the tank is located, the more speed and pressure the water will build up, the quicker it will be delivered—and the faster the fire will be put out.

Parts of a fire hydrant

Fire hydrants are just fire hydrants, right? Wrong! Here are some of the little details you might not have noticed:

1. Operating nut on top of hydrant turns main water valve on or off
2. Clapper valve just inside hydrant stops water from flowing backwards. Water can flow out of the hydrant into the hose but not in the opposite direction
3. Metal body raises water to the same height as a fire engine's water inlet. This helps to stop fire hoses from kinking.
4. Breakable bolts on base are designed to snap if a vehicle strikes the hydrant
5. Safety chain stops nozzle caps from getting lost when hydrant is in operation
6. Outlet nozzles have screw threads inside to which fire hoses can be securely attached

Photo: Key parts of a fire hydrant. Photo by courtesy of Jurek Durczak, published on Flickr under a Creative Commons Licence.

Further reading

Other articles on this website

• Fire blankets
• Fire extinguishers
• Fire sprinklers
• Fire-retardant fabrics (Nomex®)
• Smoke detectors

For older readers

• Fire Safety: US fire safety site.
• Fire kills: You can prevent it: UK fire safety site.

For younger readers

• Sparky the Fire Dog
• US Fire Administration Kids Page