Fire Hazards of Plastics
THE MANUFACTURE of synthetic resins, the basic material of the plastics industry; the fabricating of plastic products and the increasing use of plastics in building construction, all present some fire hazards. In comparison, the finished plastic product normally found in the home poses but little danger. Some examples of the hazards of the industry are covered in this installment.
Five employees were killed and more than 30 injured when a dust explosion and fire destroyed the Makalot Plastics plant in Waltham, Mass., on March 6, 1948. The force of the blast was felt for miles around and many window panes were either blown in or sucked out by the concussion.
The plant manufactured plastic molding powders for use in making dishes, radio cabinets and similar articles. Chief among the round-the-clock operations carried on were; Resin-making, hammermilling to pulverize the resins and blending to mix the powdered resins with fillers, extenders and coloring materials.
Witnesses said the whole plant appeared to burst into flames at once, shooting an enormous column of flame skyward. Minor blasts followed the first one and in a short time the fire completed the destruction. Damage was estimated at $150,000 (FIHE ENGINEERING, June 1948).
This incident illustrates one of the principal hazards of the manufacture of synthetic resins and the compounding of molding materials, as listed by the National Board of Fire Underwriters in Research Report No. 1, Fire Hazards of the Plastics Industry.
Danger of ignition sources
Another major problem in plants of this type, according to the same NBFU report, is sources of ignition in “high” hazard areas (flammable gases, vapors and dusts) such as open flame, static electricity, arcing of electrical equipment, lightning and sparks from metal contacts.
An example of this type of hazard is the recent fire in a plastics plant at Brantham, England, in which one man was killed and two others injured. In addition to making modern plastics, the plant produces a large percentage of the celluloid made in England.
The fire occurred in a department in which nitrocellulose is treated to free it from acid. The nitrated cotton linters are stored in drums, and one of these drums was being emptied into a vat in which purifying takes place. Stainless steel forks are used for scooping the material out of drums. When dry, the material is highly flammable, but it is usually worked in such a damp state that it is not considered to be easily ignitable.
Plant fire fighters using breathing apparatus recovered the body of the dead man. At the inquest, witnesses stated that following a “terrific whoosh,” the vat became a mass of flames, and burning nitrocellulose was blown around the department. This caused rapid fire spread along wooden platforms around the vats.
It has not been possible to establish the exact source of the ignition but of several possibilities, Chief Fire Officer H. F. Griffiths mentions the drying out of the nitrocellulose by a steam pipe adjacent to the vat, and ignition by a spark caused by metal to metal friction or even an electrically generated one.
Flammable liquids and gases
Hazards of highly flammable liquids and gases during processing, transportation and storage constitute another danger, according to the NBFU report.
For example, four persons were hospitalized and three others treated at the scene when an explosion rocked the new Wyandotte Chemical Company plant, 14 miles south of Baton Rouge, La., last November 25. The plant employs about 400 persons in the manufacturing of basic chemicals to use in making plastics. The explosion took place in the ethylene glycol section.
“We have no idea of what happened,” the industrial relations manager for the plant said. “It just went boom!” The blast shattered windows in the sheriff’s office at Gonzales, about five miles to the east, and was felt in downtown Baton Rouge.
Organic peroxides, sold as solids, liquids and pastes in a variety of concentrations, have in recent years found increasing use as catalysts in the plastics industry, according to the NBFU, and present sufficient hazard to have warranted the National Board to issue a special Research Report (No. 11), “Fire and Explosion Hazards of Organic Peroxides.”
This report points out that, “These active-oxygen compounds are vigorously reactive; they present explosion potentials by virtue of their thermal and shock sensitivity and their tendency to undergo auto-accelerative combustion and, in some instances, even violent decomposition. The greatest danger lies in the handling of the many different peroxides by relatively small processors or fabricators who ordinarily may not be fully conversant or appreciative of the hazards that can be presented or who may not know how to cope with them properly.”
Other hazards of the manufacture of Synthetic resins and compounding of molding powders, according to the National Board, are: Danger of hazardous chemicals during processing due to inadequate temperature, pressure and reaction time controls; failure of equipment processing hazardous chemicals due to improper design or lack of maintenance; fires caused by operational errors due to inadequately trained personnel or lack of understanding of the hazard potential of the materials involved; rapid and uncontrolled spread of fire in a plant due to improper fire protection facilities, lack of trained fire fighting personnel, and poor plant layouts, and general increase of fire hazards due to poor housekeeping and unsafe waste disposal practices. The hazards of plastics processing and fabricating are but slightly different, and are listed in the NBFU Report.
The National Board of Fire Underwriters recently issued Research Report No. 12, Nitroparaffins and Their Hazards. Among other uses, nitroparaffins are valuable solvents for synthetic resins and plastics, and are used to improve the quality of such products as polishes, cleaning compounds, vinyl resin coatings, cellulose acetate and aeetobutyrate lacquers, industrial emulsions, and cosmetic creams and lotions. Officers and inspectors, in whose districts plants using nitroparaffins are located, would be well advised to consult this report.
Rockford F. D. photo
Hazards of processing
The rupture of pipes and the failure of pumps, valves and fittings that are used to process flammable liquids and gases constitute a primary hazard in plastics processing, according to the National Board. For example, six men were felled by fumes at a Passaie, N. J., plasties plant last December 4 when a gasket on a reactor blew. The men included four workers, a fireman and a patrolman. They were overcome by vinyl chloride gas sweeping through the second floor of the plant. One worker was treated at Passaic General Hospital and released. The patrolman and another worker were kept at the hospital and listed in fair condition.
The Committee on Fire Prevention of The Society of the Plastics Industry recently issued a four-page bulletin which describes 12 fires in plastics molding and fabricating plants. Among these is the report of a fire suffered by a reinforced plastics fabricator.
This manufacturer makes plastic trays using glass mat reinforcements. Acetone, a flammable liquid, in open containers was used to clean resin from tools and the hands of employees. An employee making trays noticed flames on the floor near his feet. The fire quickly spread on
the highly combustible process waste on the floor through the tray manufacturing section of the building. This section of the building was completely destroyed.
Firemen were hampered by a lack of water near the plant. The water carried on the fire truck almost controlled the blaze, but was soon depleted. Before the pumpers could replenish their supply from a source one mile away, the fire was out of control.
The committee comments that this is another instance of locating a plant too far away from an adequate water supply. Poor housekeeping caused the fire to spread rapidly on the process waste.
Incidentally, the 1,133 companies which are members of The Society of the Plastics Industry police themselves well through the Committee on Fire Prevention. This committee faces the fire hazards of the industry forthrightly, issues informative bulletins to the members and, as in the bulletin mentioned above, does not minimize the safety deficiencies of members. The National Fire Protection Association, by the way, lias also published an informative bulletin, Occupancy Fire Record, FR 57-5, on fires in plastics plants.
Plastics in building construction
Speaking at the Fire Department Instructors Conference at Memphis in 1954, D. L. Breting, superintendent of label services, Underwriters’ Laboratories. Inc., said: “I don’t know if any of you have fought plastic fires but you are certainly going to if the use of this material continues without proper regard for the performance of plastics under fire conditions.”
Breting was speaking of the ever-increasing use of plastics in building construction and decoration. He then demonstrated a sample of material being bid on for an installation involving 500,000 square feet. “Notice,” he said, “the heavy black smoke that is released and how the plastic softens and continues to bum where it falls. This demonstration involves roughly one-tenth of a square foot of material. Can you imagine fighting a fire involving over half a million square feet?”
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Breting stressed that not all plastics are bad actors when it comes to fire. He described two plastics intended for use as luminous ceiling material, and said that when tested they exhibited one-fifth the flame spread of red oak wood.
The speaker warned that trade names have no significance in the classification of the burning characteristics of plastics. He pointed out that even the basic terms such as thermoplastic, thermosetting, polystyrene or vinyl do not necessarily indicate how the product will perform under large-scale fire conditions. He said, “Plastics vary not only in basic materials used but also in materials that may be added for specific purposes, the process by which it is formed, and the sizes and shapes into which they are formed.”
Meaning of flammability ratings
Incidentally, a warning on the burning characteristics of plastics and their flammability rating may be relevant. When you see plastics rated as low, very low, low to none, moderate or none—remember, as Mathew M. Braidech, research director of the National Board of Fire Underwriters, points out that “Much of this early work (of evaluation) has been conducted with arbitrarily established empirical test conditions, under which simple, comparative observations of ignition or burning were made.”
These tests were intended, as Mr. Breting notes, “to evaluate the hazard of plastics for small articles such as tool handles, toys, decorations and the like.” He was convinced of the inadequacy of these tests as applied to plastics intended for large-scale installations when he learned that plastic panels which put the U. L. test furnace out of commission for three days were classified as “slow-burning.”
The Second Edition of the N.F.P.A. Inspection Manual, just published, says of the ASTM test for flammability of plasties: “This test is helpful as a rough indication of relative combustibilty, but is made with very small test samples and provides no reliable information as to the behavior of the material as interior finish. It has not been adopted by tile N.F.P.A.”
In the same section, the Manual notes that plastics include materials with widely differing properties, and advises that the inspector should ask for a tunnel test rating on any structural assembly involving a plastic material in order to determine how it may be expected to behave as an interior finish.
Apropos of Mr. Breting’s findings, F. D. Lundberg, inspector, Bureau of Fire Prevention, Rockford, I11., in an article in the July 1954, issue of FIRE ENGINEERING, reported that the intensity of a dwelling fire was apparently increased by plastic tiles which had been installed on the kitchen walls and ceiling.
When the fire, started by a short circuit, reached the plastic tile, it spread so rapidly that persons who had been sitting at the kitchen table were literally chased out the kitchen door by the flames. As he went out onto the porch, the homeowner looked back at the kitchen which was then completely ablaze and to quote his words, “It was raining fire.” This effect was caused by the melting and dropping of the burning tile from the ceiling.
Inspector Lundberg observed that, “although the fire confined itself mainly to the kitchen, the entire first floor was extensively damaged due to the dense smoke and intense heat from the burning tile.”
In considering the hazards of plastics in building construction, it would be well to weigh seriously the words of Mathew M. Braidech, research director of the National Board of Fire Underwriters, “At present, the plastics industry is experiencing only “fringe” problems; as the field of building construction is entered more deeply, these will increase in complexity and number.”
Plastic consumer products
What fire hazard, if any, do small, finished plastic products normally found in the average home present? There have been cases where fabricators, for reasons of economy, esthetics or ease of fabrication, have used flammable plastics, and accidents have occurred. In general, however, as the NBFU Research Report states, “With the exception of cellulose nitrate, the plastics do not have sufficiently low ignition temperatures to constitute an unusual ignition hazard.”
Do plastics present any other hazard to fire fighters? In the next issue we shall report on what the writer believes may be the main hazard of plastics for fire fighters.
Research Report No. 1, “Fire Hazards of the Plastics Industry,” Revised Edition, 1955, National Board of Fire Underwriters, 85 John Street, New York 38, N. Y.
Fires in Plastics Molding and Fabricating Plants, Executive Committee on Fire Prevention, The Society of the Plastics Industry, Inc., 250 Park Avenue, New York 17, N. Y.
Pretty Plastics—Ugly Fires, by D. L. Breting, presented at the 26th F.D.I.C., Memphis, 1954. Published and distributed by the International Association of Fire Chiefs, New York, N. Y.
Interpretation of Flammability Evaluations and Their Application to Fire Safety Standards, by Mathew M. Braidech, Research Director, National Board of Underwriters, Journal of the Society of Plastics Engineers, January, 1959.
Research Report No. 11, “Fire and Explosion Hazards of Organic Peroxides,” 1956, National Board of Fire Underwriters, 85 John Street, New York 38, N. Y.
N.F.P.A. Inspection Manual, Second Edition, 1959, N.F.P.A., 60 Batterymarch Street, Boston 10, Mass.