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1947-48 Theatre Catalog, 6th Edition, Page 367 (353)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 367
Page 367

1947-48 Theatre Catalog, 6th Edition, Page 367

ing indoors, in a space where free entry of fresh air and rapid dissipation of the gases cannot occur, will produce a dangerous atmosphere in a matter of minutes.

When a fire occurs in a poorly ventilated space, the atmosphere rapidly becomes poor in oxygen, so that it may cause simple suffocation. Simultaneously the air is contaminated with deadly amounts of carbon monoxide and of the other poisonous gases mentioned. Fortunately, in many cases the irritating gases produced by burning cellulose and the unpleasant odor of hydrogen sulfide and so forth produced by other burning materials, may force individuals to leave the smoky atmosphere before serious harm is done. However, the presence of carbon monoxide does not become evident except by its harmful effects. This explains why fire fighters are cautioned against inhaling smoke or remaining in an atmosphere where there has been a fire, unless fresh air is available.


When a fire occurs in a projection booth, in addition to burning wood, rubber insulation, and the like, the major material involved in the fire is film. Nitrate film is particularly hazardous in a fire because it produces finitrous fumes." These fumes are dark in color, but do not have the safety factor of immediate irritation. Thus it is possible to inhale them deeply. Then, after several hours or longer, the nitric oxide which has been inhaled forms nitric acid, irritating the lungs and frequently resulting in pneumonia. This was the cause of many of the deaths in the Cleveland fire.

Since the projection booth is a rather enclosed space, poorly ventilated, the atmosphere in a fire becomes dangerous in a very short time. This is particularly so because of the speed of film fires. It is for this reason that instructions for fighting projection booth fires always emphasize the importance of attacking the fire from outside the booth.

The rapid extinguishinent of the fire is important, not only in preventing the spread of flames, but also in ending the production of fire gases. In this connection, it is appropriate to discuss the extinguishing agent in relationship to the fire gases and smoke, and, in general, its effect on the atmosphere in the booth.

When an extinguishing agent is used on a fire, it may change the atmosphere in the booth. For example, carbon dioxide still further reduces the oxygen content of the air. Vaporizing liquid contributes carbon tetrachloride vapor and other products formed when the vapor strikes the fire. Of course, the contribution of the extinguishing agent to the highly dangerous atmosphere produced by the fire itself is, in proportion, quite negligible. Since safety makes it essential that the fire be fought from outside the booth, the only important consideration is the effectiveness with which the extinguishing agent puts out the fire.


Because there is a widespread misconception about what happens when vaporizing liquid extinguishers are used on a fire, it may be helpful to clarify


the so-called ffphosgene menace."

The statement that phosgene is produced when carbon tetrachloride strikes a fire is true only under very special conditions. In the laboratory, with carefully controlled temperatures and with care that interfering substances are absent, small amounts of phosgene may be produced from carbon tetrachloride. But phosgene is very unstable and very quick to combine with other materials. It is decomposed by heat and moisture (or steam), and is absorbed by many inert materials. For example, in a set of experiments designed to produce phosgene by using carbon tetrachloride on a fire in a test chamber, it was necessary to seal the walls of the chamber with a special coating to prevent immediate absorption of the gas.

Such carefully controlled conditions are not present in a projection booth fire. The many other gases present in the atmosphere, and even the walls and equipment, would tend to destroy this highly active gas if any were formed,

In practice, when carbon tetrachloride is used on a fire, the major product

formed from the decomposition of the vapor is hydrochloric acid fumes. These fumes are very irritating, and have an unpleasant, acrid odor. By contrast, phosgene has a rather slight odor, similar to musty hay, and the inhalation of small quantities of phosgene does not have an immediately unpleasant effect. Not until several hours after phosgene has been inhaled does it affect the lungs, causing a type of pneumonia similar to that produced by nitrous fumes. .

While hydrochloric acid fumes are highly irritating, they are not likely to be harmful. A very small amount will produce an irritating sensation in the throat. It takes about thirty times this small amount of hydrochloric acid to cause any harm. The hydrochloric acid produced by vaporizing liquid when used on a fire may thus be considered a safety factor, since it serves as a forcible reminder that the fire fighter should be outside the booth before he attempts to attack the fire. In this way he will be protected from sudocation as well as poisoning by fire gases.

WITH EXTINGUISHER IN HAND, the booth. where a fire is restricted to the upper magazine, is re-entered with extreme cautionwnd always keeping the head lower than the fire and. of course, lower than the fumes generated by the tire. Here the proiectionist creeps back into the booth, in order to play the contents of the carbon tetrachloride extinguished on the fire in the upper magazine.
1947-48 Theatre Catalog, 6th Edition, Page 367