Increasing Your Fire Alarm Literacy

Increasing Your Fire Alarm Literacy

FIRE PROTECTION

Part two in a series that examines a vital link in the fire protection system.

FIRE ALARM systems can be both bothersome and mysterious to field officers and firefighters alike— though they may not like to admit it. Fire departments respond to fire alarm system calls with the belief that the alarm signifies some kind of emergency. However, the call often turns out to be a false alarm. Responders arrive on the scene and find an alarm panel displaying curiously labeled indicating lights. What should they do? What caused the alarm? Where should they look? Often the incident report cites a false alarm or a malfunctioning alarm system.

Many fire alarm system designers and installers do not keep up with the latest fire alarm system technology. As a result, systems are often designed, installed, and tested incorrectly. Long after the designers and installers are gone, the public, the fire department, and the building owner are left to deal -with faulty systems. With a minimum level of fire alarm literacy, fire suppression personnel can take the mystery out of responding to both false and emergency alarms.

WHEN A SYSTEM IS REQUIRED

State and local building and fire prevention codes and standards determine whether an occupancy requires a fire alarm system. Many jurisdictions use NFPA 101 Life Safety Code 1988 in conjunction with building codes to determine whether a fire alarm system is mandated. Fire alarm systems refer to approved NFPA 72A systems only. NFPA 72A fire alarm parts pass rigid performance tests before they may be used in a system. Systems purchased at local hardware stores usually are not suitable for industrial application of fire alarm systems as required under NFPA 72A. While there may be a UL label on these alarm boxes and components, this alone does not qualify them as approved fire alarm systems for commercial application. The UL label indicates only that the product was evaluated and complies with the applicable UL performance standards.

LOCAL FIRE ALARM SYSTEMS

The generic names for local fire alarm systems are manual and automatic. Mechanical alarm is an antiquated term with apparent origins in automatic fire sprinkler water-motor gongs. This term is no longer appropriate Modern fire alarm systems use electrical signaling and have, for the most part, few moving mechanical parts.

The following are major components of local fire alarm systems.

Fire alarm control panel. The brain, or central processor, of a manual or automatic fire alarm system is call the fire alarm control panel (FACP). Manual systems contain initiating devices that require human intervention to send a signal to the FACP. Automatic initiating devices require no human intervention. This brain center contains power supplies, power supply controllers, and one or more zone modules that tell what is happening in each circuit. Power for the initiating devices and signaling circuits comes from the FACP.

Alarm initiating devices. This broad term includes many types of detectors and activators. Heat and smoke detectors, manual pull boxes, and specialized suppression systems such as halon, carbon dioxide, and dry chemical also act as alarm initiating devices. Initiating devices are arranged in groupings called zones. A zone is an electrical circuit.

Signaling devices. Signaling devices, the “whistles and bells” of a fire alarm system, are also arranged in zones. These zones are rather simple electrical circuits. However, an initiating zone and a signaling zone may not cover the same area of the building. Signaling devices are described as audible or visible devices and include horns, strobes, flashing lights, chimes, Klaxons, and voice evacuation systems.

The nature of the occupancy determines what kind of signaling device to use. While a loud horn may be used to announce a fire alarm condition in a factory, such a device would be inappropriate in a hospital. Hospital alarm signaling must make a sound that is distinctly different from other hospital operational signals, but it also must not startle patients. A Klaxon sounding in a crowded theater can cause panic; a lessraucous signal is needed to command attention.

The type of visual signaling device used also depends on the nature of the occupancy. Flashing lights are acceptable for most applications. High-intensity strobe lights may be more suited to occupancies with visually impaired or hearing impaired people, or those with numerous flashing lights used for other purposes.

Emergency voice/alarm communications equipment. In certain occupancies, building codes and the Life Safety Code require voice evacuation signaling systems. Located in a protected room, this equipment makes verbal announcements to selected signaling zones. It is frequently found in assembly occupancies such as churches, theaters, and large auditoriums. Prerecorded voice announcements, or announcements made by a fire incident commander, are made through the voice evacuation system loudspeakers.

Some systems involve manning a room at all times when the building is occupied. A person with a microphone directs occupants to take lifesaving action when required. These systems tend to cause less panic than raucous Klaxons, horns, or bells in a crowded occupancy. In almost all voice evacuation system designs, a fire incident commander can make announcements to occupants and firefighters from this protected room.

Automatic fire sprinklers. Sprinkler systems have a primary task separate from that of fire alarm systems—specifically, suppressing fires. Nevertheless, as a secondary task, automatic sprinkler heads double as heat detectors. When hot gas flowing across the sprinkler assembly causes the head detection device to melt, the sprinkler’s mechanical parts fly apart and water flows freely out a nozzle. The water causes an electrical switch to transmit a signal to the fire alarm control panel. This electrical signal causes an evacuation, or signaling, alarm to sound as part of the fire alarm system.

Fire sprinkler systems have their own audible alarm systems. However, the purpose of the sprinkler bell is not to provide an evacuation signal to occupants but rather to notify passersby that the sprinkler system is flowing water so they can notify the proper authorities. Fire alarm systems connected to sprinkler systems notify occupants that a sprinkler system in the occupancy is flowing.

Fire alarm annunciation panel. The FAAP is a convenience device that remotely displays signals found on the control panel. Often the FACP is not conveniently located for firefighting teams entering an occupancy to see. The FAAP allows firefighters a quick look at the nature and location of the alarm. Unlike the FACP, the FAAP usually can’t be used for maintaining control over die fire alarm system.

ALARM SIGNALS TO DISTANT LOCATIONS

Some fire alarm systems only signal locally. Others also transmit signals off the protected premises and are called off-premises annunciating alarms.

An example of a local alarm application is an apartment building with 12 or more living units. Manual pull box initiating devices notify the FACP of an incident. Audible and visible signaling devices attached to the apartment building become activated for local annunciation. A hospital may be outfitted with an off-premises signaling system as well as a local signaling system. Annunciation to a remote point is accomplished in one of the following ways:

Central station service. These are located away from die protected premises. There is no technical limit as to how far away. It is not unusual for central station facilities to be located in a different city or state than the premises. The signal is sent by telephone line or special radio circuits.

Fire alarm information from an NFPAapproved local fire alarm system is sent to a separate transmitting device located somewhere on the protected premises. This transmitting device is part of an NFPA 71 system and is call an NFPA 71 transmitter. The NFPA-approved system must send three distinct types of signals to the NFPA 71 transmitter: alarm, supervisory, and trouble. According to NFPA 71, an alarm signal indicates a fire or other emergency requiring immediate action and response, including such signals as from a tripped manual box, water flow alarm, or alarm from any other automatic emergency system. The supervisory signal indicates a “need of action,” usually by onpremises personnel, including “supervision of security guards, sprinkler or other extinguishing systems or equipment, or maintenance features of protective systems.” The trouble signal is transmitted to supervisory personnel and is asociated with electrical or physical problems of the system itself.

Occasionally the distant central station electronically checks on the transmitter at the protected premises to make sure it is operating properly. This checking process is called supervision.

Qualified operators must always be on duty at the central station monitoring point. When operators receive a signal from a protected premises, they follow established procedures including notifying the public fire department.

Proprietary monitoring system. This monitoring system is located in a sturdy, secure room on the protected premises. The monitoring personnel or agency has some proprietary or financial interest in the security and safety of the complex or premises.

This system usually monitors more than one building—the protected buildings may be part of a building complex. A good example of a proprietary system is a defense plant with a highly structured plant security service. At the main security office, trained operators continuously monitor fire annunciation panels. If they receive a signal, they dispatch plant protection personnel to check out the problem. Plant protection personnel may be security personnel, a fire brigade, or both. At the same time the monitoring operator calls the public fire department on the telephone or a radio channel for assistance.

Remote monitoring system. This system monitors many buildings or occupancies at a single location, but it has no financial or operational interest in the buildings. An example of a remote monitoring system is a public fire department dispatch office that monitors the status of fire alarm systems throughout the jurisdiction. If the public fire department does not provide the remote service in a jurisdiction, the assigned remote monitoring service calls the fire department by phone or radio upon receipt of an alarm signal.

Auxiliary> monitoring systems. Auxiliary systems can be installed if a municipal fire alarm system is available. An auxiliary monitoring system consists of a local fire alarm system, located on a protected premises, connected in the street to a public fire alarm system. The public fire alarm system does not have to be a wire line arrangement. Radio fire alarm boxes on street corners can serve as part of an auxiliary monitoring system.

Consider a public school with a local fire alarm system that contains manual pull boxes and heat detecting initiating devices located throughout the school building. If one of the school initiation devices activates, a set of contacts in the FACP operates. This set of contacts is connected to the city fire alarm system through a nearby street box. The street box activates to notify the public fire department. Some municipalities refer to this fire alarm street box as a master box. The connection in the fire alarm control panel is often called the city connection.

Fire alarm systems tend to intimidate firefighters: Because they are unfamiliar with some newer systems, firefighters cannot always readily identify the real causes of alarms. They may list “false alarm” or “faulty detector” as the cause when in fact there was a legitimate reason for the activation. Friendly fire and smoke can also cause legitimate system trips—this does not imply system problems. Getting a handle on new technology and terms will help firefighters raise their fire alarm IQs.

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