Air Force Academy protected by elaborate detection and alarm system
THE FIRE PROTECTION system recently completed at the Air Force Academy near Colorado Springs, Colo., could serve as a model for fire protection systems the world over. Automatic fire detection devices, automatic extinguishing systems, manual fire alarm boxes, evacuation bells and the base fire stations are all tied together in one supervised electrical alarm plan, which protects the base housing areas as well as academy buildings and barracks.
Specified by the Air Force Academy Construction Agency, the system was designed and built by the American District Telegraph Company to meet the standards established by the National Board of Fire Underwriters for proprietary alarm systems as described in NBFU Pamphlet No. 72.
The Air Force Academy is, in effect, both an institution and a community. It is protected by its own fire department which is based at two strategic locations on the reservation. The alarm system is supervised from a master control unit at the central fire station.
Operation and maintenance
The academy fire alarm system is continuously manned by six operators from the base fire department under the command of Fire Chief C. John Riley. Two operators are on duty during daylight working hours, from eight to four. The other four operators man the central station main control unit console on four-hour shifts during the remainder of the day.
Maintenance is performed by the fire department. Trouble signals are checked out and the trouble repaired immediately, and the entire system is tested, circuit by circuit, on a regular periodic basis to insure operational readiness at all times.
Automatic alarm transmitters
The sentinels of the fire alarm system are the automatic fire-sensing devices and the manual fire alarm boxes. Over 2,500 of these units are located throughout the base. Included in this total are: Over 2,000 automatic fire detection units; over 400 manual fire alarm boxes; 60 sprinkler supervisory and waterflow alarms; and two carbon dioxide system switches. All of these are normally closed-circuit devices. When their contacts open, either automatically or manually, they initiate a transmitter which sends a coded alarm to the central fire station.
The Deteet-A-Fire units manufactured by Fenwal Incorporated, employ the rate-compensation method of actuation. Whenever the surrounding air temperature reaches a predetermined level, the units respond. They do not themselves have to be heated to a uniform temperature throughout before giving an alarm.
This type of operation is said to eliminate the time lag inherent in some fixed-temperature devices when the rate of temperature rise is slow, and at the same time eliminate the possibility of a false alarm when the increase in ambient temperature is rapid but stops short of the actual danger point. Individual detectors are set to operate at 140° F and are spaced at a maximum interval of 12% feet in the ceilings of protected buildings with each unit protecting an area of 625 square feet.
The carbon dioxide extinguishing systems are installed in the base’s two paint shops. They operate as flooding systems designed to give immediate fire protection at these hazardous locations and when tripped, the CO2 switch opens, sending an alarm.
Thirty-seven of the manual fire alarm boxes are located strategically out of doors. The remaining 400-plus alarm boxes are mounted inside various buildings. These are of the pull-lever, closed-door type. Once the lever is pulled and released, the signal of the integral alarm transmitter cannot lx* interfered with.
The fourth type of alarm-initiating device are the ADT waterflow alarm transmitters connected to the sprinkler systems alarm valves. At a preset time interval after the flow of water is initiated in the wet-pipe sprinkler system an alarm signal is transmitted to the central fire station. When water stops flowing the transmitter automatically restores itself to normal.
In addition to their function in the fire alarm system, all automatic alarm transmitters, those in the manual alarm boxes and those associated with the automatic detectors, carbon dioxide systems and sprinklers, provide telephone communications through the control unit in the central fire station. Telephone jacks accommodate portable phones which are normally used in testing and maintaining the system. However, they also provide an additional means of communications with the base fire headquarters, and through headquarters to other alarm transmitters, should radio or normal telephone circuits be temporarily inoperative.
Besides sending a coded alarm signal denoting the location to the central fire station, the transmitters actuate constant ringing, vibrating evacuation bells within the building in question. These bells sound on fire alarm signals only, not on the trouble, restoration or test signals. In most buildings the fire alarm system also shuts down air conditioning fans and other services that should be discontinued during a fire.
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AIR FORCE ACADEMY
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If the alarm boxes, detection units and other alarm-initiating devices are the sensitive nerve ends of the fire alarm system, the control and recording unit at the central fire station is its nerve center. Here, at a completely self-contained combination console and desk unit, the signals are received, recorded and retransmitted to the other base fire station and from here all alarm circuits are constantly supervised.
Transmitted code signals from the six alarm circuits are permanently recorded on paper tape. A time stamp automatically prints the date and time the alarm is received on the upper edge of the tape at the first impulse of each round of the signal. The tape becomes a permanent record of all trouble, restoration and test signals as well as all alarm signals. Four of the six circuits are currently being used in the fire alarm system. The fifth is a spare and the sixth is used to manually transmit signals to the academic fire station. It also sounds the coded alarm bells in both stations.
Should trouble occur on any of the code transmitting circuits the unit automatically conditions itself to receive signals despite the difficulty and presents a visual indication of the type of malfunction and its location through a pilot light on the panel. Trouble conditions within the console itself are also detected and indicated.
When trouble does occur, a buzzer sounds and the appropriate circuittrouble pilot light glows. A trouble reset switch is also used to test these circuits.
In case of an a.c. power failure, a storage battery immediately takes over. Rated at 48 volts and 100 ampere hours, the battery’ provides a minimum 72 hours of stand-by operation. The fluorescent lights which illuminate the console continue to function during storage battery operation through an inverter. However, if these lights are not operated during this stand-by period, the battery is capable of operating the system for at least a week. Should battery voltage fall to 80 per cent of its rated value, a buzzer and a pilot light indicate this fact.
Telephone alarms recorded
Calls received on the console’s telephone, which is connected to the base telephone system to receive telephone alarms, are recorded on a tape recorder. This is entirely automatic, requiring no operator attention during the telephone conversation. A key-operated switch in the rear of the console permits playback.
The control and recording unit at the academic fire station is a limited version of the central fire station unit. It does not contain the voice recorder or universal transmitter.
A third control panel, the Cadet Quarters Complex Control and Recording unit, receives and records alarm and restoration signals originating within the Cadet Quarters.
In conjunction with the Cadet Guard, mounted at all times in the Cadet Quarters Complex, both for practical and training purposes, the elaborate alarm system insures immediate fire control through its automatic extinguishing systems, as well as prompt response of fire fighting personnel. This combination is expected to afford maximum protection to persons and property throughout the reservation.