NOVA Online | Escape! | Escape through Time: Fire

Escape through Time
by Albert Lee and Rob Meyer

Fire | Car | Plane | Ship

Turnout Gear

"Always Ready"—This Currier and Ives painting illustrates the clothing of the early American fire fighter. The mid-19th century gear consisted almost entirely of wool, which was used both to ward off the heat of the flames and the cold of the winter air.

Turnout gear, or the protective clothing worn by fire fighters, has come a long way since the last century. In that era, fire fighters wore Civil War-style uniforms that featured heavy wool trousers, a cotton or wool shirt (usually red), and a heavy wool tunic. Wool was the obvious choice, because of its ability to shield against heat and cold, and because of its mild water and flame resistance. Rubber slickers were sometimes worn over the wool uniforms. Fire fighters brought their own gloves to the job, usually standard leather workingmen's gloves. Knee-high leather boots worn in the early years eventually gave way to rubber boots, some of which could be extended to the hips like modern waders (called "three-quarter boots").

Turnout gear took a great leap forward after World War II, when various organizations, foremost among them the National Fire Protection Association (NFPA), began issuing standards. The NFPA 1971 Standard on Protective Clothing for Structural Fire Fighting, for instance, called for an outer layer of flame-resistant fabric that would not be destroyed through charring, separating, or melting when exposed to 500°F for a five-minute period; a second layer to prevent moisture from penetrating through to the wearer; and a third layer to provide thermal insulation from radiant, conducted, and convective heat. Similar standards required gloves that could withstand flame, heat, vapor, liquids, and sharp objects, and footwear resistant to puncture, flame, heat, abrasion, and electrical current.

In the 1980s, fire fighters began wearing turnouts made of three advanced materials: an outer shell material that raised the fire resistance level to about 1,200°F before the material began to break down; a layer that allowed the fire fighter to release moisture from inside the gear; and a fire-resistant synthetic material. Ideally, the latter will last about seven seconds in a flashover situation (when all combustible materials, including walls and floors, suddenly ignite) before catching on fire, which is usually enough time for someone to bail out of room. Further, it is self-extinguishing, meaning once out of contact with a fire, it will not continue to burn. These materials have become the standard for virtually all American fire departments.

Modern protective clothing, or turnout gear, such as the Smart Coat System above, incorporates sensors to help the fire fighter assess dangerous conditions, ranging from thermal saturation to the location of a colleague who may be injured or lost in the black smoke.

Modern turnout gear has become so effective in insulating the fire fighter from heat that new equipment is now being introduced that has an internal alarm to alert him or her when the external temperature exceeds a set limit. These next-generation turnouts consist of six silicone-encapsulated heat sensors located at the shoulder, back, and chest of the turnout coat, just under the outer shell.

Finally, NFPA 1982 called for Personal Alert Safety System (PASS) devices. Fire fighters trapped in smoke-filled buildings can become disoriented as they attempt to escape, sometimes leading to incapacitation from smoke inhalation. Using small motion detectors, PASS devices set off an alarm if motion is not detected after 30 seconds.
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Helmets

An essential part of any fire fighter's gear is the helmet. Traditionally, the helmet was made of leather strengthened by the use of combs, or leather seam reinforcements. The helmet pictured above has 8 combs.

In the last century, the leather firefighter's helmet was common. The helmet's long rear brim and curled up side brims helped prevent water from running down the firefighter's neck and into his coat. The earliest leather helmets featured four combs, which are ridges of leather marking stitched seams. Theoretically, the more combs a helmet had, the stronger it was, so later helmets came equipped with eight, 12, or 16 combs.

At the turn of the century, aluminum helmets began to be popular. Though they were molded to look like leather helmets, they were cheaper. However, fire fighters quickly learned that these helmets had problems of their own. They not only conducted heat but electricity. As a result, a move back to leather helmets became inevitable. Strong enough to provide protection from falling objects, the leather helmet of the early 20th century shed water effectively and prevented objects from dropping down the back of the fire fighter's neck.

Helmet design really took off after World War II. By 1979, when NFPA issued its Standard on Structural Fire Fighter's Helmets, designers were taking into consideration a mind-boggling array of factors, including impact force and acceleration; penetration, heat, and flame resistance; resistance to electrical current; effectiveness of chin strap and suspension system; flammability and resistance of ear covers; resistance of the face shield to heat and flame; and brightness and surface area of fluorescent markings.

The modern firefighting helmet has a smaller brim but uses ear covers and a flame-resistant hood (worn underneath). Using high-tech plastics and composite materials, the helmet must be puncture-proof and resistant to heat, flame, electricity, and sudden impacts.

Beginning in the 1970s, high-tech plastic and composite material helmets came into vogue. These featured a suspension system and energy-absorbing foam impact liners; a face shield for partial eye and face protection from heat, sparks, liquids, and flying debris; flame-resistant flaps to protect the ears and neck; and a lighweight-fabric protective hood.
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Respiratory Protection

The first breathing devices used air pumped from a bellows through a hose to a "smoke mask" worn by the fire fighter. These devices were rarely used because of their bulky construction and unreliable performance. World War I led to the introduction of the gas mask proper. A few fire departments began to make these available to fire fighters in limited numbers, even though most did not protect well from carbon monoxide, and none worked in an oxygen-deficient atmosphere.

In the 1920s, the U.S. Bureau of Mines commissioned the design and introduction of "rebreather" devices for mine rescue, and these were eventually adapted by the fire service. Rebreathers mixed a small stream of pure oxygen with exhaled air, which had been passed through chemicals that removed a portion of the carbon dioxide. These early rebreathers were better than their World War I predecessors but were clumsy, fragile, and difficult to control. In addition, the oxygen bottles for air supply were costly, and extensive training was necessary. As a result, they were seldom used by fire fighters.

The World War I era saw the emergence of the first self-contained breathing apparatus, or SCBA (not to be confused with self-contained underwater breathing apparatus, or SCUBA). The devices featured metered compressed breathing air, which was sent directly into the face mask. As with the earlier rebreathers, however, there were drawbacks for fire fighters. SCBAs were expensive and uncomfortably heavy, adding to the fatigue and strain of fire prevention.

World War II pilots used oxygen breathing systems in high-altitude flights, which led to the development of open-circuit, positive-pressure firefighting SCBAs (self-contained breathing apparatus).

Before World War II, most SCBAs were closed-circuit rebreathers, which did not rely on the local atmosphere to supply breathing air or dissipate exhaled gases. But following the war open-circuit SCBA became the norm. The advance was based upon breathing oxygen systems used in high-altitude aircraft, where compressed oxygen was supplied by high-pressure cylinders through regulators and half facepieces to individual aircrew members, either on demand or through continuous flow.

In 1981, the National Fire Prevention Agency issued a standard on modern SCBA systems mandating positive pressure airflow at 100 liters per minute and a minimum service life of 30 minutes.

In the 1970s, the U.S. Occupational Safety and Health Administration required the use of positive pressure SCBA for firefighting. By maintaining a small amount of pure oxygen in a mask at all times, positive pressure above ambient prevents toxic smoke and gases from entering the face mask and being inhaled. A 1981 NFPA standard for SCBA mandated, besides positive pressure, a minimum service life of 30 minutes and 100 liters per minute airflow.
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Thermal Imaging

The use of thermal imaging cameras may improve the ability of the future fire fighter to navigate in a smoke-filled room to find potential victims or to pinpoint areas in the walls or floors that may have been weakened by the fire.

Smoke and darkness no longer inhibit the fire fighter from seeing the thermal image of a fire—and its potential victims. With the help of thermal imaging cameras, fire fighters can detect the slightest variations in thermal energy, even at extreme temperatures. A smoke-filled room contains millions of minute carbon particles, which block visible light as effectively as a wall. But since infrared travels in longer wavelengths than visible light, infrared cameras can see right through smoke. These cameras display their readings of infrared in variations of gray. Objects devoid of heat appear black; warm or hot objects appear white. These devices also help fire fighters detect stress points—signs of a potential flashover, for example, or floors that have been dangerously weakened from a fire below.
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Albert Lee is Originations Production Assistant and Rob Meyer is Online Production Assistant, respectively, at NOVA.

Photos/Illustrations: (1) Museum of the City of New York; (2) SunnyCor Inc.; (3) L-W Book Sales; (4,6,7) NOVA/WGBH Educational Foundation; (5) Corbis Images, Hulton-Deutsch Collection.

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