CODE & STANDARD REFERENCES
What is Emergency Voice Alarm Communication?
Today, we will be discussing emergency voice/alarm communication systems, otherwise known as EVACS.
Detailed requirements for EVACS are provided in NFPA 72 Chapter 24. Our discussion today is at the 10,000-foot level to provide an overview of a voice system.
REQUIREMENTS IN THE IBC
Voice systems are becoming more common with every new code cycle. The IBC Section 907 currently requires EVACS systems for the following:
1. Assembly occupancies with an occupant load of 1,000 or more.
2. Educational occupancies with more than 100 occupants.
3. Special amusement buildings.
4. High rise buildings.
5. Atriums within a Group A, E, or M Occupancy.
6. Deep underground buildings.
7. And Covered mall buildings.
In our series FA101, fire alarm requirements in the IBC which can be found in the content library under the fire alarm category, we discussed the drivers for a fire alarm system are based upon the number of occupants, capability of the occupants and the height of the building.
It is clear EVACS systems are required for large occupant load buildings, buildings where the occupant load may not be capable of evacuation without assistance, and very tall or very deep buildings.
Now, let’s break down the term EVACS as it pertains to notification appliances:
EMERGENCY VOICE (EV)
Emergency voice (EV) – where Notification is by voice, as opposed to a standard horn. This brings about the term “intelligibility,” with the simplest definition of intelligibility being: can you understand what the voice instruction is telling you to do? We will get into the science and testing of voice systems as referenced in NFPA 72 in a future course on speech intelligibility, for now, the goal is to ensure that you can understand what the voice message says.
The female voice has been shown to be more effective and intelligible, (not accidentally, but with real research to back this up), this makes sense we have been listening to our mothers since birth…
Alarm (A) – Although the notification from speakers is an intelligible voice providing directions, all EVACS systems are still required to meet the audibility requirements of NFPA 72 Chapter 18, therefore all voice messages must be preceded by an audible tone which is 15 decibels above ambient throughout the entire building.
Did that tone sound familiar?
You guessed it, the preceding tone is a temporal code 3…
COMMUNICATION SYSTEM (CS)
Communication system (CS) - EVACS systems have prerecorded messages which include fire evacuation as the primary, in addition each system will have a microphone located at the fire alarm control unit or remote local operator console where emergency first responders or authorized personnel can make live voice announcements to provide communication directly to the entire building or sections of the building.
The main feature of an EVACS system is to provide a clear voice message to occupants of the building with instructions on what they need to do through speakers and speaker strobes in a calm environment as opposed to a loud alarm without instructions which can cause panic.
Different spaces have different acoustical characteristics. Does a closet full of linens sound differently than an open grain silo? Of course, they do. Many factors play into acoustical characteristics of a space. The concept of acoustically distinguishable spaces is unique required for EVACS systems. During design, we evaluate whether or not a space will be required to be intelligible, and make provisions accordingly.
Intelligibility is required in spaces such as conference rooms, open offices and corridors but it is not required in mechanical spaces or individual (private) offices; the goal is for occupants to be alerted by the audible tone, then to proceed into the general circulation where they can clearly understand the voice instructions.
When we have temporal-3-only systems, we generally refer to these systems as horn/strobe systems. With emergency voice alarm communication capabilities, we generally refer to these as “voice” or “EVACS” systems.
In summary, EVACS systems are becoming more popular as a design choice based upon the effectiveness of a voice message to provide a calm and clear instruction for what to do during an emergency. An EVACS system cost more than the traditional horn strobe system due to the amplifiers and number of speakers required for intelligibility, however the benefit of emergency communication either by pre-recorded or live announcements far outweigh the cost.
In our next video, we will discuss low frequency notification.
Until next time, I’m Al Yakel and this is MeyerFire University.
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