Carbon Fibers Raise Fireground Problems
DEP. CHIEF ELMER CHAPMAN
New York Fire Department
Carbon fibers were produced nearly a century ago in the search for an incandescent lamp filament. During the 1950s and ’60s, experimentation resulted in stronger fibers and the use of their special strength properties in new materials called composites.
These materials, which are composed of carbon or graphite fibers (the difference being the temperature of pyrolysis during manufacture) embodied in a resin binder, have opened a wealth of new structural engineering and consumer product opportunities. In the next decade, composites may become as important to the United States economy as the steel and aluminum they replace. No other material now in prospect offers equivalent advantages.
The potential benefits of composites are manyfold. Higher strength and lighter weight military and commercial products portend energy savings and increased safety. Unfortunately, these benefits are not realized without risk. The carbon/graphite fibers used in the present generation of composite materials are finer than human hair (8 micrometers diameter, 6 milimeters length), extremely good electrical conductors, and virtually indestructible.
They are so light that millions are contained in a gram mass. If released in air, they can easily be transported by wind or currents. In contact with electrical devices, they can create resistive loading, short circuits and arcing, which results in stoppages and/or destruction. A variety of actual incidents can be cited supporting the hazards the fibers pose to electrical equipment.
Their health hazard has not been fully ascertained and require careful research and analysis before any firm conclusions can be reached. At current manufactured diameters and lengths, carbon or graphite fibers are primarily an irritant to eyes and skin, like fiberglass, rather than carcinogenic or destructive to lung tissue.
The current uses of carbon/graphite fibers worldwide entail about 700,000 pounds of material. At least six countries are currently manufacturing composites and fabricating them into products. The major use today is in military and commercial aircraft as structural components, such as tails, slats, fairings, wings, rotor blades, spoilers, flaps, etc.
The list of consumer products is growing daily to include such items as skis, fishing rods, golf clubs, tennis rackets, CB antennas, hockey sticks, bats, etc. The major anticipated use is in automobiles, where weight reductions are necessary to achieve fuel economy. This can be achieved by replacing steel and aluminum with composites.
Inadvertent fiber release, during manufacture or by destruction of the resin binder in fire, is the major hazard associated with the composites. Major manufacturers are aware of the potential problems associated with these materials and have applied controls to avoid inplant problems. With the growth expected in the use of these materials in aircraft, automobiles and consumer products, any accident resulting in fire involving these materials becomes a substantial possible source of fiber release. Further, the uncontrolled incineration of these materials and of discarded consumer products can create serious problems.
On May 12, 1972, during a cleanup of an area in the Union Carbide’s fiber production building at Fostoria, Ohio, a carton containing untwisted filaments of fine strands of carbon fibers was inadvertently placed in the plant incinerator. Subsequently, fibers emitted from the stack spread over the surrounding area. The electrically conductive strands settled on several electrical substations and caused short circuits and power outages at two substations about half a mile downwind from the plant within a half hour of the incineration. Additional substation failures were reported as far as 3 miles from the plant, and there were reported power outages that afternoon which darkened most of the downtown area of Fostoria east of Main St.
What can the fire service do to minimize the probability of electrical failures when these materials are involved in accidental fires? At the present time there is very little instructional material available to the fire service to assist in formulating procedures to handle this type of incident. Knowledge of the potential can go a long way in limiting the release of the fibers by using tactics which do not agitate the debris and cause additional release of the fibers into the atmosphere.
Some procedures that can be utilized are as follows:
- Extinguish the fire as quickly as possible.
- Do not overhaul the debris.
- Cover the debris with protein foam to trap the loose particles.
- Ensure that all personnel working in and around the area wear protective breathing apparatus, gloves and complete protective clothing to limit the exposure of skin to these fibers.
- Cover the area with heavy-duty polyethelene wrap or similar disposable material to prevent any futher release of the fibers.
- Call the local office of Defense Civil Preparedness Agency for additional assistance.