Fire-Fighting Hazards of Battery Stations
What Hazardous Materials Are Present in Stations—Cells Unattended at Night—Some of the Dangers—Question of Extinguishing Agent
FIRES in battery stations contain hazards which are peculiar to themselves, and certain precautions must be taken by firemen in handling such fires. The following paper gives some very important information on this subject and should be kept as a matter of reference and study for fire departments which have this class of risks to handle.
I am informed that there has been current a statement, that in battery stations, such as have come into frequent existence by reason of the extended use of electrical starting and lighting equipment on automobiles, there resides an extraordinary hazard to firemen by reason of the chemicals present, on account of possible reaction between them and extinguishing agents.
In considering this matter, it is first necessary to establish what is probably present in the average station, what hazards to firemen are connected therewith, independent of fire extinguishing agents, and then to determine what if any hazards are added by the use of the various means of fire extinguishment.
Ordinary Lead Plate Storage Cell
The most common battery used in automobile practice is the ordinary lead plate storage cell, although a few Edison storage batteries are used and some of the battery stations carry a supply of dry cells for the ignition renewals of customers using oldfashioned dual systems.
The storage batteries usually consist of from three to twelve cells, connected in series and enclosed in a wooden box which has been liberally treated inside with resinous pitch, and the same material is used to seal the tops and edges and is carried in stock for such use.
The lead battery contains one group of lead plates loaded with lead oxides, and another, which is principally spongy metallic lead, the electrolyte is sulphuric acid and water showing a specific gravity of from 1,000 to 1,300, according as the battery is discharged or charged.
The Edison battery has plates of nickel and iron with copper oxide or some similar material for filler and electrolyte is a rather strong solution of caustic soda.
Dry cells are usually small zinc containers in pasteboard cartons, containing a carbon electrode surrounded by manganese dioxide, with an electrolyte of flour paste, containing ammonium chloride and zinc chloride solution.
Other Materials Present
There will probably be present in such a station a liberal supply of distilled water and of sulphuric acid, diluted to the strength required for filling new or overhauled batteries and possibly part of a carboy of strong acid, a supply of new battery plates, both positive and negative, a collection of old discarded plates waiting to be junked and a supply of sealing pitch. There may be a small supply of asphaltum or P. B. paint for painting boxes and terminals and some solvent or thinner for such materials.
If Edison batteries are handled, there will probably be a supply of caustic soda and possibly a few plates of both polarities.
There will be means of charging batteries; these will vary all the way from a small private plant generator, operated by a gas engine to a motorgenerator converting the public power supply. The various intermediate alternatives comprise lamp banks or other resistance for cutting down a d. c. supply, such as the 500 volt railway current or the 220 volt d. c. Edison; mercury arc, kenotron, aluminum and vibratory rectifiers. Usually there will be a maze of slack temporary criss cross wiring, and the floor will be sufficiently acid-soaked to be a pretty fair conductor.
Cells Frequently Left Unattended at Night
Cells are put on charge and frequently left unattended over night, overcharged cells give off oxygen and hydrogen, both non-poisonous. and if the room is small, and not well ventilated, these gases might accumulate in sufficient quantity to form an explosive mixture; but such occurrence is uncommon, although there is often enough in a battery to pop if a spark is applied to the vent. These gases always carry a small amount of ozone and enough small suspended vesicles of sulphuric acid to afford the well-known pungent smell of a battery room, even enough to cause personal discomfort when there is some ventilation.
Hazards Before Application of Extinguishing Agent
The direct fire hazards of such a place are too wellknown to you for me to dwell upon here, so I will assume one has caused a fire and pass to the hazards to firemen previous to the application of any extinguishing agent.
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Fire Hazards of Battery Stations
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There is the hazard of electric shock, due to the possibility of a breakdown in the current translating device, allowing the outside high voltage to get through to the battery circuit. This is enhanced by the condition of the wiring and of the floor previously noted.
I here is the hazard of the breaking of a carboy of strong acid, either by the heat of the fire or by inadvertence of entry in the smoke. The more dilute battery acid is destructive of clothing and unpleasant on the skin but is not very dangerous externally.
Where mercury arc rectifiers are used, there is a slight possible danger of mercury vapor poisoning but this would presuppose the breakage of a tube under load immediately before or during the near presence of the firemen. I consider this a remote hazard.
There is the hazard of heavy batteries falling on one’s feet, due to the entangling wires and the frequent insecurity of the batteries on the charging racks; although not serious, I consider this real and unpleasant.
There is also the hazard of battery acid happening to spill into a place sufficiently hot from the fire to become vaporized. Unless it happened while the men were present, I doubt if they would ever go into such an atmosphere without a mask. The somewhat similar atmosphere existing when charging has been carried on without ventilation has been previously mentioned.
There is no particular hazard to dry caustic soda, a solution of it is common soap lye, whose action is well-known to you. Some stations have hydrogen generators or tanks of it, with oxygen also in separate tanks for lead burning; the hazards of this are the same as where oxywelding is done.
The paint and solvent hazard here would be no different from anywhere else.
Possible Products of Combustion
Now as to possible products of combustion; sulphuric acid, distilled water, metallic lead in its ordinary form, lead oxide, nickel, iron, sal ammoniac, manganese dioxide, zinc chloride and caustic soda are not inflammable. Dry spongy lead will sometimes take fire spontaneously but it gives off no material amount of gas:—lead oxide, the product of such combustion is a solid. Zinc can lie made to burn but it too gives no serious amount of gaseous product, and the total amount present even in a gross of drv cells is trivial.
The insulation on the numerous wires, and the sealing pitch, both on battery tops and in stock for use. would seem to be the most inflammable substances present that would differ from the average store fire. I he amount of smoke and gas that can be evolved from even a small quantity of wire insulation is well known by reason of experiences in citv subways and ducts where power wires have burned their insulation. The products of combustion from the sealing pitch and that from the insulation are almost the same, and would not be materiallv different in a battery station from what they would produce burning elsewhere. Any difference would be due to the heat of their combustion vaporizing the acid in close proximity, which has been previously discussed.
Main Question of Extinguishing Agent
Let us now take up the main question of extinguishing agent. It is assumed that the extinguishing agents likely to be used are fresh water, salt water, calcium chloride solution, soda and acid, and carbon tetrachloride.
Fresh water can cause no chemical hazard, except by a stream of it happening to strike into the open top of a carboy of strong sulphuric acid. The danger of pouring water into strong acid is well known. There is some electrical hazard in case the stream strikes high tension electrical apparatus.
Salt water is practically no different from fresh water, except to increase the electrical hazard. A small stream of salt water striking hot sulphuric acid will give off muriatic acid gas. but as salt water is rarely used, except in a large stream from a fire boat, or high pressure line, this is not worth consideration. In passing I would say that muriatic acid acting on lead peroxide will make some chlorine.
Addition of Calcium Chloride and Tetrachloride
Calcium chloride solution is like salt water, but as it is used in the small stream of an extinguisher, there may be some muriatic acid gas produced; this is a very corrosive, irritating gas, but has no quick acting poisonous qualities unless very concentrated. Soda and acid as discharged from the ordinary extinguisher into a fire consists of a solution of sodium sulphate containing usually an excess of unconsumed, dissolved sodium bicarbonate (although with careless recharging the acid may be slightly in excess) and charged with carbon dioxide gas. There is no reaction possible between either the sodium sulphate, the unused bicarbonate or possible excess sulphuric acid and the materials found in the battery station which would cause any hazard different from ordinary. The electrical hazard is the same as with the previous agents. Foamite will add no hazard if it happens to be used.
Carbon tetrachloride (and the compounds of it under various trade names), does not possess the electrical hazard of the others, but it has all its usual disadvantages when used in a confined space. When shot into a dry fire, it produces quite a lot of its own vapor and the vapors of other similar chlorides of carbon which are anaesthetic but not particularly poisonous and some chlorine, phosgene and muriatic acid gas, although extended tests have shown that if water is not simultaneously used, the quantity of the extremely poisonous phosgene is not serious, unless the space is very limited.
With high temperature, and the presence of vaporizing water or sulphuric acid, the quantity of phosgene and muriatic acid would unquestionably he greater, and I would recommend caution in using any great quantity of such extinguisher, unless the ventilation is good. However, there is nothing to fear from carbon tetrachloride shooting into any of the chemicals in the battery station, unless they happen to be highly heated. When used on burning electrical insulation, it seems to render the already nauseating smudge of that material more so; hut it is extremely doubtful if it adds anything dangerous in marked degree, except in a very confined space. An ordinary army gas mask should he effective against everything except illuminating gas which is not peculiar to battery stations.
My conclusion therefore is that in tackling a fire in a battery station, look out for the physical and electrical hazards, observe the same precautions with carbon tetrachloride you would in any space of similar size and ventilation and you need not worry about any extraordinary hazard introduced by your extinguishing agents.
From a paper read before a meeting of the Fire Chiefs’ Club of Massachusetts.
In answer to one question Mr. Buchanan stated a man might get a dose of phosgene gas and might be all right, but two weeks after it if he ran upstairs his heart might be affected and he would have to be very careful about over-exerting himself. He also stated, in answer to Chief Rich’s question as to the gas masks used and their safety in the presence of phosgene gas, that some of the masks in use are safe in such cases and some are not. Chief Doyle asked as to the nature of the gas formed by burning zinc, which is done to clean soot out of chimneys, to which Mr. Buchanan replied, “Zinc is one of the rather volatile metals in that its boiling point is not far above its melting point and the gas is composed partly of zinc vapor and partly of zinc, oxide vapor and precipitates itself on the walls of the chimney. You might burn up some dry cells which contain considerable zinc and there might be a good deal of ammonia around from the sal ammoniac inside the battery but there would be no danger from the zinc.”
Chief Toomey inquired as to whether or not there were found to be any set of rules in battery stations posted up either by themselves or the town or city authorities, to which Mr. Buchanan replied that in the one or two stations where he had been there was nothing in the way of rules.