Integrated, Sure. But is it Intelligible?
Combining MNS and EVACS means new challenges for fire inspectors.
NFPA Journal®, May/June 2009
The 2010 edition of NFPA 72®, National Fire Alarm and Signaling Code®, is up for adoption during NFPA’s Fire Safety Conference & Expo® in Chicago in June. Once again, the code will change, presenting more challenges than ever to those responsible for inspecting and accepting new fire alarm system installations in their jurisdictions. The name change alone provides a hint as to one of the major changes to the code, which now includes a separate new chapter on emergency communications systems.
This new chapter contains the requirements for traditional, in-building fire emergency voice/alarm communications systems (EVACS), but new operational requirements for in-building and wide-area mass notification systems (MNS) have also been added. For the first time in history, the code allows you to combine or integrate in-building fire emergency voice/alarm communications systems with other communications systems such as MNS and public address and paging systems. In addition, certain mass notification messages can take precedence over a fire alarm signal, also a first for the code.
Another radical change in this chapter allows the EVACS to provide background music and operate as a paging system, in addition to using it as an emergency MNS. The technology is now available to ensure that fire alarm or priority mass notification messages, as determined by a risk analysis, will take precedence over any other announcements from nonemergency systems. Speaker systems are available that incorporate volume controls and components that allow occupants to lower or turn off the speakers in their areas but switch back to their required power output when the fire alarm system or MNS is actuated.
As the use of integrated EVACS and MNS continues to increase, inspectors will be challenged to ensure that their intelligibility meets the code requirements, something that designers, installers, and authorities having jurisdiction struggled with in earlier editions of the code. Designers, installers, and fire inspectors should understand the importance of having a good distribution of speakers throughout an area rather than trying to use a higher power output of a few speakers. As the new annex material in Section A.24.3.1 states, “In certain situations, it is important to provide a distributed sound level with minimal sound intensity variations to achieve an intelligible voice message. This differs from past fire alarm design practice that used fewer notification appliances, but with each having greater sound pressure output levels.”
To determine proper speaker distribution compliance during the plans review, fire inspectors will need a basic understanding of sound and communications principles to ensure that, at a minimum, all occupied places designated as acoustically designed spaces (ADS) have a speaker or proper speaker distribution to meet the challenge of intelligibility.
The technical challenges the new code presents fire inspectors are many, and they will need additional training to understand these new requirements in order to do their jobs efficiently and ensure that code-compliant fire alarm systems are installed in their jurisdictions.
Wayne D. Moore, P.E., FSFPE, is a principal with Hughes Associates and immediate past char of the NFPA 72 Technical Correlating Committee.