The Exhibitor (Nov 1938-May 1939)

BM-10 otherwise interested must be constantly alert and informed in order that the reasonable demands for fire prevention and protection are complied with. Foremost among these interested parties is the fire department. The fire chief, his officers, and, in fact, the entire personnel of the department must be possessed of at least a working knowledge of these special hazards if fires involving them are to be handled intelligently. "In general, the commercial air-conditioning system consists of a means of supplying fresh air, commonly referred to as the 'fresh air intake’; a filter for purifying the air by the removal of foreign materials; a water spray for the air, if necessary; a heat unit for drying or dehumidifying the air when required, and for heating purposes during the winter months; a chilling or refrigerating unit for cooling purposes; a combined blower or fan combined with a system of ducts for carrying the conditioned air to the various rooms or spaces. "It is obvious that, if, in the winter months, all of the air is taken from the outside, the fuel cost for raising the temperature of the air, or, in brief, heating to requirement, will be excessive. By the same token, if all the air during the summer months is taken from the outside, the cost of cooling it to the required degree will be excessive. For these reasons, it is the practice to recirculate the air in summer and winter, operating with all doors and windows normally closed, and depending for a secondary fresh-air supply upon what is termed 'infiltration,’ that is, the air which filters in through window and door casements. In large spaces of public assembly, it is sometimes necessary to supplement this supply of fresh air by additional air from the outside. "In order to take advantage of the principles of recirculation, the duct system must be designed and installed to provide for it. This is accomplished in the following manner: "The duct system is arranged in two divisions. On the discharge side, a duct may supply a single area, but usually a main duct extends vertically through the floors, with a horizontal branch duct in each story, extending from the main vertical duct. By means of opening at intervals in the horizontal duct, the conditioned air is discharged into the room or space where air conditioning is supplied. "There is no physical connection between what is termed the 'return duct’ and the 'discharge duct,’ except through a connection to the fan or blower. The return duct, for returning the air through the fresh air intake to the filters and other conditioning equipment for a repetition of the cycle, is usually a vertical duct passing through all floors on the side of the building opposite the discharge duct. "As the conditioned air enters a room or other space, it sinks to the floor and enters the return duct through grilled openings near the floor. 'If the reader has used his imagination, he has already conceived what would happen if a fire started in the basement, or, in fact, any room served by the air-conditioning system. In his mind’s eye he has watched the fire quickly spread throughout the entire building by way of these vertical stacks and their flue-like action, augmented by the velocity of the air created by the blower. It follows, then, that such a system of ducts, unless adequately safeguarded, will greatly increase the fire hazard, and render fire-fighting operations extremely difficult. "The question is how can this inherent hazard be reduced to a reasonable and acceptable degree? The answer can be found in the BETTER MANAGEMENT regulations of the National Board of Fire Underwriters. "Let us first consider the duct systems and the means whereby a fire, having gained entrance thereto, may spread to the rooms or areas served by the air-conditioning system. "Obviously, these means are the discharge openings in the horizontal branch ducts and the openings near the floor in the return ducts. As a means of protection, dampers are required in the horizontal branch ducts at the point where they connect to the main or vertical discharge duct, and at each point where the branch duct passes through a fire partition. Similarly, dampers are required at all openings in the return ducts. All dampers must normally be in the open position and so secured by a fusible link or some other approved heat-actuated device. In brief, the dampers must be arranged to close automatically in case of fire. "So far as the ducts are concerned, they must be of non-combustible construction. Linings are frequently installed to deaden or eliminate the sound due to vibration or from other sources which might otherwise be transmitted through the ducts. These linings must be of fire-resistive material. Similarly, filters must be of material possessing sufficient fire-resistance to prevent the support of flame and the propagation of sparks. In other words, every effort must be made to prevent fire from gaining a foothold on the materials entering into the construction or equipment of the duct system. "An example in point is the fire of December, 1934, which occurred in the ducts off the air-conditioning system of the Srtand Theatre, New York, New York. The fire was also of unusual interest because of its unusual origin. The refrigerating machinery was located in the basement of an adacent building and cold air was forced by a blower in the basement of this building through a sheet metal duct. This duct emerged through the pavement of a 15 -foot wide exit court, between the theatre and the adjacent building, extended across the court to the north wall of the theatre and continued along this wall and also the east wall. Small branch ducts extended from this duct on the theatre exterior and discharged through high ventilating openings into the auditorium section. The duct on the exterior side of the theatre walls was lined with a flammable insulating material, consisting of one layer of pressed wall board. "At approximately 5 P. M. a considerable quantity of rubbish in the court between the theatre and the adjacent building began to burn, but that was extinguished. This rubbish was piled in a corner formed by the west side of the air-conditioning duct and the south wall of the building adjacent to the theatre. "Smoke was noticed in the theatre soon after the fire in rubbish was extinguished. The smoke increased in intensity and the audience was asked to leave. Evacuation was accomplished without confusion. "An examination showed that the fire in the rubbish had caused the flammable insulating or lining material on the duct interior to ignite. This may have been caused by the conduction of heat through the metal walls of the duct, or by direct communication through small openings at seams where the sheet metal of the duct was fastened to the angle iron frame. As the air-conditioning system was not in use at the time, the fan or blower was not in operation. The duct lining apparently smouldered for some time, but eventually all of this material in the duct was burning and the smoke, hot gases, and sparks were discharged into the auditorium section of the theatre through the numerous branch duct openings, igniting balcony seats and furnishings and blistering the wall and ceiling finish. The fire was eventually extinguished, but not before heavy damage was done because of the delay in locating the source of the fire. "Aside from demonstrating the fire hazard of flammable duct lining, the fire indicated the need of constructing such exterior ducts of brick or tile and the installation of automatic dampers at branch duct junctions with the main duct and under such conditions at outlet openings. "In commercial type systems, cooling of the air is obtained by refrigeration, the air, after humidifying, br dehumidifying, being blown over refrigeration coils. If a flammable or irritant refrigerant is used, it is not permissible to place the evaporator or coils containing the refrigerant in the air-conditioning duct. The reason for this should be obvious, as any leakage in the refrigerant would permit the refrigerant to pass through the airconditioning system and into the rooms or other spaces served. This could readily bring about a fire and, in the case of a place of public assemblage, such as a theatre, a panic. If such refrigerants are employed, the refrigerating machine must be placed in a separate compartment, meeting the requirements of the A. S. A. Safety Code for mechanical refrigeration, and a brine circulated to a coil in the air-conditioning duct and over which the air may be blown. On the other hand, if the refrigerant is non-inflammable, non-toxic, and non-irritant, the direct system of refrigeration may be employed, that is, the evaporation coils containing the refrigerant may be placed directly in the duct system. For this purpose, refrigerants placed in Groups 5 and 6 by the Underwriters’ Laboratories Report on the Comparative Life, Fire, and Explosion Hazard of Common Refrigerants may be considered as meeting these three requirements for safety. "The heating unit for heating the air must be installed in compliance with the requirements for heating apparatus, that is, the usual requirements for non-combustible foundation and clearance of smoke and hot air pipes from combustible materials. 'We come now to an especially important unit of the air-conditioning system, the blower or fan. It is this unit which forces the conditioned air through the system to the rooms or spaces served. It is apparent that if a fire develops in the ducts while the fan or blower is in operation, its intensity will be increased and what might otherwise be simply smouldering material or sparks would be fanned into flame. For this reason, there must be provided an automatic means for stopping the fan or blower in the case of fire; this requirement may be met by some form of automatic heat-actuated device. Furthermore there must be a remote control for the device, so that in any emergency, the fire department can shut down the system without difficulty. A study of this general problem clearly points to the urgent need of complete knowledge on the part of the fire department concerning, first of all, the exact location of the remote control of the fan or blower, and in addition the character of the refrigerant employed, and the location of the automatic dampers. In brief, it demonstrated the need of frequent fire department inspection in order to acquaint the personnel with the essential features of the system.” Thank you, Mr. Newell. • INSURANCE RATES are of interest to all exhibitors, and the following summarized remarks of H. E). Rice, manager of the New York Fire Insurance Rating Organization, as given before the Air March 15, 193 9