Fire communication equipment is used to contact guests and patrons during an emergency and also to assist the fire fighters in communicating with each other. One of the ironic tragedies of fire deaths and injuries is that frequently they are avoidable.
Smoke and panic kill far more people than heat and flames do enunciator panels, or intercoms, allow frightened potential victims to be contacted by calm voice that can give them life-saving information. If a qualified person does not arrive at the command center in time, a taped announcement may be used.
Here again this equipment is being used more frequently because it is mandated by government regulation, but these regulations are not consistent. Some states require that the telephone system wiring be used; other states prohibit its use: a similar kind of possible double use can be affected with the in-house background music system.
(i) Fire wardens’ phones-Phones located in locked red boxes-may are used by fire fighters to communicate with the command center, other fire fighters, or with everyone in the area over the public address system. Thus this communication link can help with both evacuation and fire fighting.
(ii) Jacks (similar to electrical outlets) may be installed in strategic areas, such as stairways: each fire fighter will have a handset that can be plugged into the jacks.
(iii) Alarm devices may also be considered communication equipment even though the communications is only one way and may convey little information beyond the fact that something is apparently wrong.
Alarm “messages” may now be routed to selected people or destinations (not all alarms are general alarms), and they may also indicate the general area of the problem. Alarms may be either manual (a person must pull a switch) or automatic (set off by a detector).
(iv) Several types of alarm devices designed specifically to alert handicapped guests are now on the market. TTY telephones can help communicate with the hearing-impaired by printing out the oral message coming over the telephone line.
Visual alert systems can detect sound or vibration such as knocking on a door and trigger a visual signal such as a blinking light. Escape route maps can be prepared in Braille to help blind persons find escape routes. The presence of handicapped guests can be recorded in logbooks or noted by flagging mailboxes so fire fighters can be quickly informed,
(v) Containment equipment-devices that retard the spread of smoke or fire. The purpose of ventilation equipment is to move air around so that air remains fresh and clean throughout the building. In a fire situation this beneficial service can become deadly if the system allows the toxic gases generated by a fire to be spread.
Thus fire dampers are installed in air ducts to stop this infiltration. Unfortunately, the dampers are frequently triggered by heat and thus allow considerable smoke to spread before they close off circulation; ‘ some dampers will also leak smoke.
The building’s ventilation can also be controlled by some sophisticated systems that lower the pressure in surrounding rooms, thus slowing down.
Fire Alarm Apparatus:
The majority of fire alarm contact devices depend for their action upon the expansion of metals when subjected to a rise of temperature. In some forms a composite strip is used, made up of two metals having dissimilar coefficients of expansion.
The two strips are firmly secured together at both ends, one of which is fixed, whilst the other is arranged to make or break contact with an adjustable contact screw.
Heat causes the two metals to expand unequally, with the result that the strip distorts c buckles, and either makes or breaks contact with the screw.
A similar result is obtained with a single metal strip, anchored at both ends, and a contact arranged at its centre point. The bowing of the strip consequent upon expansion functions in the same manner as previously.
“Aero” fire alarm system:
It makes use of the expansion of air. A system of small bore copper tubing is installed throughout the premises to be protected, and coupled up to a central closed chamber or series of chambers, each fitted with a flexible diaphragm, carrying contact-making device.
Increase of air pressure within the system, set up by local heating of the tubing at any given point, raises the air pressure in the corresponding chamber. These forces the diaphragm outwards, causing the contacts to operate, and thus complete an alarm bell circuit.
Provision is made for gradual expansion, such as would ordinarily occur with the normal temperature changes during the day or night, or with the seasons: in the shape of leak valves, which permit air to pass into or out of the system at such a rate that the alarm will remain unaffected save by a sudden or abnormal rise in temperature.
Fire Alarm Circuits:
There are two alternative methods of working either a fire or burglar alarm installation: viz, (ii) “open” and (ii) “closed” circuit, (i) Under the former the alarm is given by the contact devices automatically closing a circuit which includes a bell or other indicator, and the necessary battery.
This system is fairly reliable, but calls for systematic testing and inspection to ensure that it are in thorough working order at all times.
(ii) With the “closed” circuit or permanent current system, on the other hand, the various alarm contacts are normally closed, and current is always flowing in the main circuit, which includes a relay winding. The relay is normally energized, and holds its armature permanently against the pole pieces.
Should a contact break, or a wire be cut or disconnected at any point in the system, the current is at once interrupted, the relay armature falls back under tension of a spring, and, by so doing, completes a local alarm bell circuit.
It will be seen that this latter system, although involving a greater current consumption that the former, is far more reliable, in that it is self-testing at all times, any disconnection being at once signaled by the ringing of the alarm bell.
Closed circuit working entails a slightly higher grade of insulation on the line wires, owing to the constant potential which exists between different points, and might in time set up leakage were the insulation at all weak or defective.
Fire alarm systems, local protective signaling system, aurally protective signaling system, Remote station protective signaling, proprietor protective signaling system.
Multiple Dwelling Fire Alarm Systems
A hotel would utilize a supervised dual coded system with automatic stations in store room, kitchen, boiler room & other unsupervised areas.
Non-coded system Master coded system Zone coded system Dual coded system Selective coded system per signaling system.
A signaling system may be used in hotels. Sprinkler transmitters & an inundation and smoke detectors in the ducts, achieving an engineered smoke control system whose primary purpose is to prevent the spread of smoke through the building. Smoke detection in corridors is also normally required.
Presaging or coded bells are installed in office of the building engineer as well in that of the hotel managers.
The fire alarm panel is most often placed in the mechanical equipment area. Single station smoke detection in each room/suit. Connected to the central system & annunciated. In lieu of individual floor annunciation over the door lights & floor inundation can be used.
A voice communication system in high rise building is desirable.