FIRE LOSS MANAGEMENT

FIRE LOSS MANAGEMENT

A Series by

DISASTER MANAGEMENT

Part 6: UNFRIENDLY CAUSES UF FIRE, CUNTINUED

LAST MONTH I discussed lightning, static electricity, and arson as some examples of unfriendly causes of fire—forces and actions that in and of themselves serve no purpose. Spontaneous ignition and metallic sparks are two other principal causes of unfriendly fire. Again, the best way to prevent fire disasters is by recognizing that these causes exist and manipulating extension and management.

SPONTANEOUS IGNITION

Spontaneous ignition is an often misused term. Spontaneous ignition can result from spontaneous heating of certain materials and, in a few cases, from heat derived from chemical decomposition. It is an extremely difficult phenomenon to demonstrate, particularly with ordinary materials, but it can happen.

Practically all materials will oxidize or combine with oxygen to some extent. This combination generates heat, but the rate of normal oxidation of organic materials is so slow that the heat is dissipated. However, certain combustible materials oxidize and retain the heat until they reach ignition temperature. Whether or not they retain heat depends on a number of factors. In some cases the various factors involved are mutually contradictory. For example, air is required for oxidation, yet a good flow of air will remove the heat developed by the oxidation. When spontaneous ignition is a hazard there are two possible approaches: exclude most or all air, and thoroughly ventilate to remove generated heat.

Organic materials. Materials subject to spontaneous ignition are of animal or vegetable origin. Mineral oils, such as lubricating oils generally used for motor vehicles, and gasoline are not subject to spontaneous ignition. Vegetable oils such as tung oil, linseed oil, and peanut oil, many of which are used in painting, are subject to spontaneous ignition, particularly when the oil is combined with a material that acts as a wick, providing for a greater oxidation area and an ignitable kindling.

For this reason the rags and clothes of painters using oil-based paints are a particularly serious source of spontaneous ignition. When conditions are conducive to spontaneous ignition, the addition of external heat accelerates the process. A bunch of oily rags that might be safe in a damp, cool basement might ignite very readily in a sun-baked attic. During World War II, hemp cargo nets and sand bags waterproofed with linseed oil started many fires.

Soft coal is a common element subject to spontaneous ignition.

(Photos by author)

Inorganic materials. In some cases materials not prone to spontaneous ignition at normal temperatures spontaneously ignite when subjected to elevated temperatures over time. Typically this is the case with foam rubber that has been heated by an ordinary household clothes dryer. If a fire occurs in a dryer, the dryer’s structure can often contain it. However, foam rubber clothing pads that have been in a dryer can ignite some time afterward. This makes them particularly dangerous, because if the fire occurs after the clothes have been removed from the dryer, the fire’s extension may be much more severe.

In one case a woman dumped the contents of the dryer onto the bed where her infant was sleeping. She returned a short time later to find the clothes in flames. Fortunately, she was able to rescue the baby.

In another case, a woman placed her laundry on an easy chair while she went out shopping. Shortly afterward, neighbors saw flames in the house, rushed in, and extinguished the fire. Fire investigators determined the cause of fire to be a padded bra.

At a multiple-alarm drug store fire that was being overhauled, I walked between two aisles of polyurethane pillows, which were not on fire. When I returned soon after, they were starting to burn. The heat of the fire had preheated the pillows to the point where their temperature continued to rise. Thus, newly manufactured polyurethane is isolated for a period of time because of its tendency to ignite spontaneously.

Cellulose nitrate. Spontaneous heating of such materials as cellulose nitrate, or nitrocellulose, is caused by the heat of decomposition above a certain critical temperature. Nitrocellulose starts to decompose and liberates heat that accelerates decomposition. This can cause spontaneous ignition of the material.

Prior to 1952, motion pictures were printed on nitrocellulose film. This film caused many serious fires and fatalities, as one or two breaths of nitrocellulose fumes can result in death or permanent disability. In 1929, 125 people died in the Cleveland Clinic fire from the fumes of nitrocellulose x-ray film in the basement.

Today studios worldwide use cellulose acetate “safety film.” While there is much old film still in storage, it eventually deteriorates and must be transferred to acetate film or will be lost forever.

However, the dangers of nitrocellulose are not widely known, even among some in the scientific community. Recently a university professor of plastics included nitrocellulose as a possible plastic for use in buildings. In another incident, an alert inspector found nitrocellulose tubes containing hospital blood samples. The label didn’t mention toxicity. It is not overly imaginative to think that in some storeroom there may be a large quantity of these tubes intermixed with other combustibles. If this is the case, another Cleveland Clinic disaster is in the making.

Chemical reactions. A violent chemical reaction between certain chemicals and water or air is another example of spontaneous ignition. Some chemicals, such as phosphorus, ignite almost immediately when exposed to air. Other materials such as sodium react violently and explosively with water. When handling or using such violently and rapidly reactive materials, take extra precautions to avoid the possibility of reaction altogether or to contain an unavoidable reaction. For example, avoid applying water in any form to sodium metal. If this is unavoidable, consider the safety of personnel first and foremost.

While most metal shavings and turnings generally do not ignite spontaneously, uranium metal does. Uranium metal is characteristically handled under oil or water, not simply wet with oil or water. Ignition often occurs when shavings or turnings accumulate in an oil bath and then build up above the surface of the oil. The ignition most often takes place where the pile of uranium chips meets the oil’s surface.

Uranium chips or turnings stored under oil or water may also ignite if a leak in the drum causes the oil or water level to drop, uncovering the uranium. This spontaneous heating is accelerated if the material is stored in the sun during the summertime.

Control the extension. If preventing spontaneous ignition is not practical or is impossible, focus on controlling the possible extension. At one facility, despite regulations, rules, and good procedures, the mere presence of rags, clothing, and drying oils for oil painting operations made avoiding a fire caused by spontaneous ignition almost impossible. So the facility supplied the painting department with a number of gypsy carts. Painters stored, used, and mixed all painting materials in the carts. Over time there were quite a few fires in the gypsy carts, but the carts prevented the extension of the spontaneous ignitioncaused fire to the rest of the building. If providing carts is not practical, at least recognize the hazard in the area to be painted, and designate a place for the storage and mixing of paints that would contain a fire. The area should be very accessible to firefighters. Keep in mind that fighting the fire may result in water damage to the designated area. This is an example of how to manage a fire problem, and if a fire occurs, the report should note that it was a “managed hazard.” Water-based paints, of course, eliminate this hazard.

(A list of materials subject to spontaneous heating can be found in the NFPA Fire Protection Handbook Table 5-11J, pp.5-130. Consult the index for several other references.)

METALLIC SPARKS

Metallic sparks are similar to static electricity as a fire cause. Usually such sparks are very small bits of heated metal that can ignite only gases or dust.

Sparks from a grinder fell into the open hatch of a tank in which hydrogen gas was being generated; the resultant explosion injured 67 people. “Tramp metal”—scraps of ferrous metal that create sparks—is a constant hazard in grain elevators because of the combustible dust. The same tiny spark that ignites the gaseous fuel in a cigarette lighter is capable of igniting a huge tank.

This cut-off saw can produce a fatal spark if flammable dust or gas is present.

Use nonsparking tools where flammable vapors are present. These tools are made of copper hardened with a beryllium alloy so that no sparks occur when the tool slips. Heavier sparks, such as those produced in cutting and welding operations, can ignite solid fuels.

FRIENDLY-UNFRIENDLY CAUSES

Friction and smoking can be considered friendly or unfriendly causes of fire, depending on circumstances or point of view.

Friction. Boy scouts know that friction can start fires and that the American Indians started fires by rubbing two sticks together. Friction-caused fires occur in vehicles, freight cars, and elsewhere when intense heat develops from two objects rubbing together. Such fires often result from lubrication system failure or holding some material against a moving wheel accidently.

Belt-driven machinery is a common source of friction-caused fires. Very often fans or compressors are driven by several belts; when one belt breaks, it can fall free or catch underneath the other belts. In this latter case, the friction will cause the belts to ignite.

Again, if prevention of friction-caused fires is impossible, concentrate on controlling extension. Shield continuously running machinery that uses multiple belt drives from any kindling. Then if a friction-caused fire occurs, the fire will be limited to the belts.

Smoking. Smoking and smoking materials — matches, lighters, and lighter fluid—are responsible for many fires; however, “smoking” is often carelessly listed as a fire’s cause when the cause is really “unknown.”

Where smoking is prohibited entirely, we must undertake a rigid program of inspection and surveillance. In ammunition plants, for example, workers are required to surrender their lighters, cigarettes, and matches before entering work areas, and owning or possessing any of these materials in the operating areas is cause for dismissal. At such locations smoking areas are provided where it is safe to smoke and electrical igniters are installed. With such a total system, there is no excuse or sympathy for the person who “sneaks a smoke.”

Management that posts “no smoking” signs but provides no supervised smoking area and that penalizes those caught smoking invites smoking in hidden areas where a fire will burn undetected. Matches and cigarette butts in out-ofthe-way areas prove that “no smoking” regulations are being violated. They probably will be violated in this manner until a safe smoking area is provided or management decides to enforce the “no smoking” regulations rigidly and police illegal smoking areas. A controlled smoking system is most desirable. Airlines have countered the problem of passengers smoking in rest rooms by installing smoke detectors. The alarm sounds as soon as a match is lit.

Look at the manner in which cigarette butts and rubbish are removed, especially at the end of the business day. A church hall was destroyed after a party because the volunteers gathered up all the paper tablecloths, paper napkins, and cigarette butts into one rubbish container and then left it in a place where destruction was inevitable once the fire started. The contents of ashtrays should be removed so that they are not intermixed with combustible materials. The dumping of ashtrays into wastepaper baskets is a good way to put together the cause and the kindling.

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