4  FM quick reads on fire alarm

1. Low-frequency Sounders More Effective at Rousing Sleepers

Low-frequency fire alarm sounders are now required in sleeping quarters, as first called out in NFPA 72, 2010 edition. This requirement applies to new construction of hotel rooms, college dorm rooms, or bedrooms in apartments or assisted living facilities.

The low-frequency sounders are 520 Hz, square wave. This frequency was found to be more effective in awakening people with hearing loss. The frequency is also more effective at waking children, who tend to have deeper sleep than adults and can sleep right through high-frequency strobes.

Volume levels were not modified at all by the change in the standard. In addition, the low-frequency sounders are required only in the sleeping quarters; common areas such as hallways or lobbies do not require the low-frequency sounders.

Another application of the 520 Hz, square wave frequency is that is the required tone that precedes voice notifications in a an emergency communication system.

To learn more about the considerations that went into the NFPA 72 low-frequency sounder requirement, click here.

Capitalize on Fire Alarm Systems Advanced Communications Capabilities

As fire alarm system technology continues to advance, facilities that rely on older systems may miss opportunities to improve important aspects of fire/life safety performance or to solve problems that older systems cannot address.

One benefit of new fire alarm system technology is improved communication. Combine the powerful information provided by field detection devices with the ability to capitalize on high-speed data transmission provided by fiber optic transmission media, wide-area and local-area networks, and you have fire alarm systems capable of sending very detailed information via Internet-based digital alarm communicator transmitters or direct networks to emergency responders or off-site monitoring locations with device specific detail.

Because the fire alarm industry knew little of professional sound and communication principles, early generation voice communications systems provided unintelligible notification messages that were solely used for fire alarm functions and fire department operations. The voice communications component of fire alarm systems has evolved to the point that specifically routed messaging can deliver clear emergency and non-emergency messages, including music. This change required the fire alarm industry to realize that redundant voice communications systems, like PA systems and music systems, could be replaced by fire alarm voice communications systems. Codes in place require the industry to supervise speaker circuits for integrity in the active state. In other words, while music is playing, the fire alarm system must be capable of identifying that a circuit has been damaged or broken. Today this capability is now commonplace for the major fire alarm system manufacturers.

Over the last 10 years, fire alarm systems have begun to evolve into multi-faceted mass communication platforms, largely as a result of terrorist events and government or military needs. These mass communication capabilities include fully intelligible voice messaging systems that can integrate textual signage. Multi-faceted mass communication plans can now draw on the fire alarm system to provide message outputs via text messaging, paging and email. Additionally, fire alarm systems can be seamlessly integrated with wide area mass notification systems that use high-power outdoor speaker arrays that can reach large geographical areas with highly intelligible messages.

Fire-Alarm and Detection Systems Areas of Concern

There is a whole range of common problems with fire safety systems, which underscores the importance of regular inspections. Common issues inspectors find during testing include non-operational equipment or equipment that does not operate as originally installed, according to such parameters as sound-pressure levels and detector sensitivity.

Other issues commonly encountered include: systems that have not been maintained properly, such as not cleaning detectors in harsh environments; system modifications that are not code-compliant and, as a result, hinder system performance and integrity; and poor system installations and modifications.

A lack of knowledge about the system, improper documentation, and improper component and circuit labeling also can pose problems during testing. Also, accidental discharges of fire-suppression systems, such as clean agents and deluge sprinklers, can occur if the service company is not aware of specific system functions or does not follow proper testing protocol.

The age of a fire-alarm and detection system also can pose problems during testing. Systems that are 15 years old and older might have lived out their performance lives. Testing systems of this age typically uncovers problems that include equipment that no longer functions properly, defective components requiring replacement, and poorly maintained equipment.

Addressing system problems can be as simple as replacing faulty components, repairing wiring and conducting routine maintenance. Using competent, experienced fire-alarm contractors for system installations can reduce future problems resulting from poor installations.


fire alarm , low frequency

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