Consulting-Specifying Engineer - February 2008 - (Page 14)

M/E Roundtable The concept of continuing to use the fire alarm system to also alert occupants of potential danger other than fire is both cost effective and efficient. If a building already has a fire alarm system, it is typically relatively easy to add mass notification components. Also, the priority of mass notification messages and fire alarm messages are easier to address if the programming is within a single system. KOFFEL: During the design of a fire alarm system, if system expansion capability is provided, it is usually done to accommodate future building growth or interior renovations. Proper system design can allow for modifications to systems without compromising the integrity of the system. CSE: Does the specifying of alarm device types and location tend to be prescriptive in the codes, or do designers have considerable latitude in these designs? NIELSON: Prescriptive code requirements and the competitive bidding processes normally drive device and appliance selection. KOFFEL: In general terms, yes. It should be noted, however, that system designers do have a certain degree of latitude; an example would be a performance-based alternative approaches to visual notification device coverage and detector coverage, which NFPA 72 permits. We also are seeing more consideration for fire alarm performance as part of equivalencies and performance-based designs. Ask the experts: FA systems in assisted-living centers Every month, Consulting-Specifying Engineer editors ask a distinguished panel of experts for information about how to best solve your problems, challenges, and new engineering issues. At www.csemag.com/asktheexperts, CSE gives its readers and Web visitors the opportunity to pose questions directly to the panelists. Below is a question for February’s topic, specifically about fire alarm and mass notifcation systems. We’ve recently upgraded our fire alarm system during a renovation of an elderly housing complex. The tenants fear that the new decibel level of the apartment horns will cause panic and possible fright (enough to cause a heart attack). It has been suggested that we may be able to lower the apartment horn decibel level about 10 dBA, but it would require the approval of the fire department here in Boston—outcome doubtful. What is a solution?” —Michele G. Sdougas, facilities manager, Brighton, Mass. WILLIAM KOFFEL: Assuming the new fire alarm system was designed per the Life Safety Code and/or the IBC, the required sound pressure levels should fall between 70 and 120 dBA. Both codes require the audible devices to be 15 dBA above the average ambient sound level or 5 dBA above the maximum sound level having duration of at least 60 sec., whichever is greater. Assuming an average ambient sound level of 55 dBA, the devices could potentially be adjusted such that 70 dBA is measured in every occupied space within the complex, with 75 dBA at the pillow. If concerns persist despite these measures, and visible notification devices are provided throughout all occupied areas of the complex, the next course of action could be to approach the authority having jurisdiction and request a reduction/elimination in the audible signaling requirements, per application of Section 7.4.2.2. An experience encountered by our firm involved the opposite response from tenants. During two recent high-rise residential sprinkler and fire alarm design projects, the building owner conveyed several existing complaints by elderly building occupants not being able to hear the existing building fire alarm system activate. These tenants were happy to see new fire alarm systems being provided in their buildings and have not voiced concerns over anticipated sound pressure levels. RODGER REISWIG: Apartments typically use small piezo electric-type sounders for fire alarm notification. These sounders often are manufactured to create sound audible levels of high 80 dBA to the low 90s dBA. The “mini horns” typically used in apartments operate in the high frequency range of approximately 3,100 Hz. The Fire Protection Research Foundation commissioned research studies that have found that the elderly and very young do not respond consistently to these higher pitch devices. The foundation is sponsoring further research but preliminarily has found that lower pitch devices in the 500 Hz range tend to wake the elderly and very young more quickly. Regarding the “fear” of the tenants that the fire alarm sound will be too loud and frightening, the opposite concern would be if the sound was not loud enough, it may not provide an opportunity to alert a sleeping person of fire danger. So, it is a delicate balance. NFPA 72 requires a minimum sound level of 75 dBA at the pillow level in sleeping areas and a minimum sound level of 70 dBA in other areas. Turn to page 36 for an article on how assisted-living centers safeguard an increasingly aging population by complying with the Life Safety Code and other safety measures. “ 14 Consulting-Specifying Engineer • FEBRUARY 2008 http://www.csemag.com/asktheexperts

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Consulting-Specifying Engineer - February 2008 Contents Viewpoint News M/E Roundtable How To Write Control Sequences Mentoring Engineers: Myths, Motivations, and Models Keep Young Electrical Engineers Grounded Protecting a Vulnerable Population Codes & Standards Case Study New Products Equipment Lifecycles Advertisers Index Green Space

Consulting-Specifying Engineer - February 2008

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