Fascinating. Probably 99.9% of my experience is in educational theaters, and I've worked in quite a few. Every single one that I have ever worked in had a fire alarm that rings with the whole building and no sort of automated life
safety system. Even in at the two schools that built new theaters in 2008 and 2009. I'm wondering if the state of Washington ignores these particular codes or just what the deal is. Like I said
Brad I'm not trying to argue with you, it's just that what you are talking about is so different from anything I've ever seen up here.
No argument either way, in fact I'm very interested to hear any details regarding where someone had an
AHJ approve their using the
house audio
system and how they addressed some of the related concerns.
I'm getting into territory outside my expertise but my understanding is that assembly spaces typically require either audible alarms (Code 3, slow whoop,
etc.) or an Emergency Voice/Alarm Communication (EVAC)
system that reproduces recorded messages as well as audible alarms. Certain conditions related to occupancy, height,
etc. may require an EVAC
system. This may explain why some people encounter such systems and others do not.
If your life
safety system includes audible alarms or a voice evac
system, then in my experience the
AHJ may require muting or disabling the
house sound
system when a life
safety alarm occurs in order to prevent the
house system from potentially interfering with or reducing the effectiveness of the life
safety systems.
Since EVAC systems have to incorporate live announcement ability, if you have an EVAC
system then using that would seem the preferred option for making any announcements. You theoretically could use a
house sound
system as an EVAC
system, however I believe that it would have meet all of the related requirements for that use (monitored, on emergency
power, required levels and intelligibility and so on) and be tested and approved for the use, something that would apply to very few systems not designed specifically for that purpose.
An example of why a dedicated
system is usually desired is that one would want to know that the announce
microphone is always 'live' and that there is as small a chance as possible that it may have been unplugged, muted, repatched (probably even more of an issue with virtual patching in digital consoles), had the
gain turned down, is not routed to the right outputs and so on. If you were to use the
house system you would want some way to minimize all of those possibilities and to assure as much as
practical that if you had to use the announce
microphone in an emergency it would work as intended. And that might entail something like the announce
microphone going direct to an input on the
system processor rather than to the mixing
console with a
contact closure from the life
safety system causing the
processor to
enable the announce input and
mute all other inputs.
So the only way I see using a typical
house system for announcements during a life
safety event that seems to fit into the
NFPA scheme would be as a supplemental
system to the life
safety systems. In other words, it may be used to provide additional information as long as it does not interfere with or negatively impact the life
safety system alarms or annunciations. And that being allowed or desired, and if so any conditions or limitations involved, is something you would want to verify with your insurer,
AHJ,
etc.
But this is just all my interpretation based on my experiences and what others have told me, I welcome any related information or insights that anyone has to offer.
