International projectionist (Oct 1931-Sept 1933)

June 1933 INTERNATIONAL PROJECTIONIST 13 duce heat and give off vapors, even in the absence of air. The temperature at which a piece of motion picture film catches fire in the air is about 320 degrees F., according to the Du Pont Film Manufacturing Corp. The gaseous products of combustion vary widely in character according to the amount of oxygen readily available. In the absence of air, nitrocellulose film starts to decompose at a measurable rate at about 212 degrees F. The rate of decomposition increases rapidly as the temperature rises, several cubic feet of poisonous gases being produced per 100 feet of film. When these gases are mixed with a limited amount of air the mixture is explosive. There is, however, no danger of a serious explosion unless large quantities of film are being stored in a relatively small space. In the regular course of operation, with approved types of machines, the picture remains exposed for only about one twenty-fifth of a second, and the degree of heating produced is well within the limits of safety, the temperature being far below that at which the decomposition of the film becomes measurable. 2. Light Sources Light sources used for moving pictures consume from a few hundred to eight thousand watts each. Typical reflectors direct from 30 to 70 per cent of the available energy into the beam; lens systems about 5 to 20 per cent. Only a small amount of the radiation is absorbed in the film. According to tests made by the Du Pont Corp., samples of stationary film left exposed in a projector fitted with 900;watt incandescent lamp were ignited in three to four seconds. The U. S. Bureau of Standards found that with carbon arcs ignition of film took place in from one-half to one second. 3. Nature of Accidents Due to the Ignition of Nitrocellulose Film When a film takes fire in the projection room, the spread of the fire and the escape of fumes into the auditorium may alarm the audience and possibly cause a serious panic, even though the actual danger from fire or explosion be small. There is also the possibility of panic if the audience becomes aware through the image on the screen that the film has caught fire in the projector. As a rule, the only appreciable danger is to the projectionist, who may be burned or overcome by fumes in trying to extinguish a film fire. 4. Cause of Fire A few projection room fires occur each year in Canada of such a nature as to completely interrupt the performances. The provinces of British Columbia, Alberta and Ontario combined, with 530 theatres, had 11 film fires in projection rooms during 1931, and five or six in 1932. (As a comparison, the city of New York, with about 550 theatres, had 22 such fires in 1931, and 24 in 1932.) Of 46 fires reported in Ontario as having occurred in projection rooms from 1929 to 1932, 29 were caused by the film breaking or stopping due to defective sprockets, poor patches, etc., two by failure of the fire shutter, three through defective equipment and one by poor lubrication of new film. In addition, 11 film fires were caused by carelessness; in six of these one projectionist and one apprentice were present, and in only one case two qualified projectionists. Of 24 fires reported from British Columbia for the years 1927 to 1932, inclusive, 14 were caused by the film breaking near the light aperture. 5. Improvement of Machines and Films The dangers involved in the projection of motion pictures have long been recognized and steps have been taken to reduce them by improvements in machines and film, the adoption of fireproof construction and devices for smoke — control, and last but not least, -proper trainbig of the ■projectionists. (a) Safety Devices on Projectors In practically all machines, the film is protected by an automatic shutter which shields the film when it is not moving at the proper speed. While tests made show that it closes in ample time to prevent ignition of the Committee Personnel The personnel of the committee formed by the National Research Council of Canada to inquire into and report upon projection room regulations and practices is: H. M. Tory President, National Research Council F. C. Badgley Director, Canadian Government Motion Picture Bureau B. C. Ballard Assistant Research Physicist F. E. Lathe Director, Division of Research Information, National Research Council R. H. Manske Associate Research Chemist J. H. Parkin Assistant Director, Division of Physics and Engineering R. RUEDY Research Investigator film when the machine slows down, it is useless in the case of a film jamming or coming apart near a patch. For such an emergency a handoperated shutter is provided. In addition, some machines have foot brakes. In order to prevent the fire from being carried into the magazines, metal rollers are placed near the points where the film leaves the upper, or enters the lower, magazine. Experience shows that at the speed at which the film is moving these fire snuffers do not always stop a fire. The appearance of the image of the fire on the screen can often be prevented only by the quick action of the projectionist, who closes the hand shutter and interrupts the light. (b) General Improvements in Projectors and Films With the discarding of the separate sound record and the automatic adjustment of the proper sound level obtained from the film, the projection of sound motion pictures has been relieved of much of its burden. The additional risk involved in increasing the film speed from 60 to 90 per minute, in changing from silent to sound films, is largely offset by the necessity of discarding sound films while still in good mechanical condition. The use of more intense light sources is compensated at least in part by the introduction of rear shutters and by the shorter time each picture remains exposed to the light source during normal operation. It is impossible, however, to ignore the fact that with the high-intensity arc the film will ignite much sooner, in the event of stoppage. Moreover, the service engineers sent out by equipment manufacturers now inspect the projectors at frequent intervals. Decided improvement has also been made in the quality of the film. (The trend undoubtedly is toward a more and more mechanical operation. By means of devices similar to those used for the reproduction of sound an automatic safety mechanism protecting the film from the light in case of accident might be developed. A safety film has been developed, but has not yet come into general commercial use.) 6. Regulations Regards Projection Rooms and Machines (a) Fire-Fighting Equipment Practically all persons in responsible positions consulted on this question consider the portable fire-fighting equipment ordinarily provided in projection rooms as of very limited usefulness for fighting film fires. Experiments carried out by the commit