“Chlorine Fires” and Pool Chemicals
Chlorine is an elemental gas that is very reactive. It is greenishyellow in color and has a characteristic penetrating and irritating odor. In commerce, chlorine is compressed to its liquid form for transportation in barges, railroad tank cars, tank trucks, and cylinders under 100 psig pressure. Liquid chlorine is clear and amber in color. In both gaseous and liquid forms it is nonexplosive and nonflammable. It is a powerful oxidizer and will support a fire almost as efficiently as oxygen. It is corrosive and is toxic when present in sufficient quantities.
Actually, most chlorine emergencies in warehouses do not involve chlorine stored in either the liquid or gaseous state but rather a family of solid chemicals, commonly used in swimming pools, that react with water to liberate chlorine. The chemical involved in the Springfield fire was Trichloro-s-triazinetrione, also called Trichloro(iso) cyanuric acid. Salts of this chemical form a group of compounds with available chlorine levels of 55 to 90 percent. It allows the pool owner to take the chlorine home in a safe, easily transported manner. The chlorine is released when the pool owner adds the chemicals to his pool. It’s therefore quite useful for the pool owner but is a potential storage problem for the fire department.
Any spilled material should be cleaned up as soon as possible to prevent contamination with other substances with which it may react; for example, floor-sweeping compounds should not be used. Keep spilled material dry. If allowed to stand in wet, damp areas, gases that are highly irritating to the eyes, mucous membranes, and respiratory tract may develop. Its dust is also irritating to the mucous membranes. Firefighters should wear SCBA, and full turnout gear should be worn to protect moist, exposed skin from the dust. Where there are high levels of gases present, impervious or vapor-tight clothing is strongly recommended. Chlorine concentrations of 1,000 ppm for even a brief period may be fatal. Remember, chlorine does not readily disperse in air because it is 2½ times heavier than atmosphere.
Chlorinating compounds are not combustible per se. If heated to the range of 220 to 260°C, they will decompose with the generation of heat. The intensity of the heat produced is sufficient to ignite paper, wood, or the fiber storage drum. Any thermal decomposition of these compounds will produce a cloud of white gases. This smoke is noxious and creates visibility problems.
There are two basic methods of controlling heat from thermal decomposition and extinguishing resultant fires:
- quenching with very large amounts of water; and
- isolating the decomposing material and allowing it to be consumed itself and the chemical process to end.
Selecting the optimum method to extinguish a chlorinating compound decomposition will depend on the grade and type of the compound, the extent that decomposition has progressed, the amount of material involved, accessibility, water supply, and whether an area that’s isolated from both the population and a source of fuel exists close by. Consultation with a qualified member of industry is recommended. If one is not available, CHEMTREC should be able to provide additional information as well as establish an industry contact. For more on the hazards of chlorine, see Frank Fire’s Chemical Data Notebook Series in the July ’86 issue of Fire Engineering.
