are school cafeteria dining areas (average size) required to have at least three nas? the schools i went to had three nas in the dining area of the cafeteria. i’m just referring to the dining area of the cafeteria, not the kitchen or the teacher’s lounge.
Like any other room in the building, signal coverage depends entirely on the size of the room. What may be an average-sized room to you may be larger or smaller to other people.
For instance, my elementary school had only two Integrity signals, each on walls opposite each other.
In my first middle school, there were four 9838 horns ceiling-mounted somewhat equidistant from each other, as the cafeteria was essentially a large square room.
In my second middle school, there were four ZNS signals, but the cafeteria was arranged in an odd two-level orientation, with stairs and ADA ramps connecting the two halves.
And in my high school, because the cafeteria connected to the main foyer and stairwell, the ceiling was very high and required several ceiling-mounted ZNSs to cover.
I’ve been inside school cafeterias that only had one NA for the entire dining area and those were large open space dining areas. They were old alarms however, and so I think it is something that was grandfathered.
It all depends on how large the room is and that is what leads to the decision of how many alarms are put in the room. My elementary school cafeteria was also the gymnasium so there were 4 9838 horns with there being two of each on the longer walls. Now there are 8 SpectrAlert Advance speakers in there with there being 2 on each wall.
My middle school had 2 4051 horns on the back wall where you first come in from the corridor.
My high school cafeteria which was also the auditorium had 2 9838s next to two of the four exits to the corridor.
My middle school cafeteria (built in 2008 and remodeled in 2015), only had two N/A’s, so I can’t imagine it’s a code requirement, at least in the state of Minnesota. It’s a pretty large cafeteria as well.
It depends on ho loud the horns are. My high school cafeteria was pretty big because it was also the auditorium and it had four exits into the corridor. There were only 2 9838 horns next to of the exits. I was only in there 3 times when they went off and one time while they were testing the alarms and they got the job done.
My high school, built in 1969, had four cafeterias (the main classroom building was divided into four sections by color), each one rather medium-sized, and each had four Simplex 4040 horns. It was NOT fun when I was in there one day and the alarms went off.
My first elementary school (kindergarten) was built in 1974 had three Simplex 4051+4050-80 horn/lights in its’ cafetorium, which was actually kind of open and had the main lobby and office across from it. A fourth alarm was right outside the main office, but it wasn’t visible from the cafetorium. To be fair, this cafetorium was fairly large.
My second elementary school, built in 1971, had NO visible alarm signals in its’ cafetorium; there were a couple of Federal Vibratone 450 horns (Gamewell FlexAlarm system) in the stage area, but they could barely be heard over the students talking and when the curtains were closed. This cafetorium was around the same size as the previous one.
My middle school, built in 1957, had a slightly smaller cafeteria, with only one flush-mount Federal horn in it (another old Gamewell FlexAlarm system.)
It seems to depend on the size of the cafeteria, or when the school was built or the alarm system was installed. I remember with the middle school near my house, they used to have one Edwards 380-L flush-mount Adaptahorn in their cafeteria, from when the school was built in 1954. During the 2003 renovation, two Simplex TrueAlert speaker/strobes were installed, with one across from the other.
It’s purely based on size since 90’s. Before that it was based on whatever someone felt like, meaning there were no real requirements. That’s why in older schools you might see 10 devices in the entire place.
Today, strobe coverage dictates all. The size and physical floor plan determine the amount of strobes. Correct me if I’m wrong, but I recall reading that there must be one strobe per every 20’ x 20’ area. My high school has TEN SpectrAlert Advances, 5 P2R’s on High Volume Temporal, and 5 SR remote strobes (I can’t remember the candela settings) in the dining room, and a P2R and SR in the serving line. As for the kitchen, I’ve never been in there so I have no clue. The rest of the school has a mix of SpectrAlert Advance P2R’s, SR’s, PC2R’s, and SCR signals run by the semi-reliable Silent Knight IFP-2000 installed when the school was built in 2009. That cafeteria gets rather LOUD during fire drills. :lol:
As for grandfather clauses, if the existing layout, wiring, etc. does not change, the existing coverage (or lack thereof) is deemed sufficient unless the AHJ says otherwise. My 6th grade middle school only had one System Sensor MA sounder in the dining room set on Swept Frequency, run by an ESL 1500, and the roar of 200 talking middle schoolers proved no match for the obnoxious whine of Swept Frequency. My 7th/8th grade middle school only had one Wheelock 34T in the dining room and only one in the kitchen, but the both of them did their job WELL during a mid-lunch malfunction of the fault-ridden Fire-Lite MS-5210UD that controlled them.
I think it also probably depends on the installer. The Simplex/Standard Electric Time and ESL (the latter two now Fire-Lite) systems in schools I’ve been a student in, both old and new, seemed to use the least amount of signals possible, while the EST and Silent Knight systems seem to have signals EVERYWHERE. One of my elementary schools had 6 EST Genesis horn/strobes per hallway, plus in every classroom and bathroom, while the other two I went to had TrueAlerts or 2901-9838+4903-9101 horn/strobe-plates spaced well apart. The school with TrueAlerts had 4 per hallway, with remote strobes in every classroom/bathroom, and 2 horn/strobes in the Cafeteria (4020 system installed in 2001), and the school with 9838+9101’s had 2 per hallway and 1 in the rather small Cafeteria (4005 system installed in 1990 as a 4002).
So basically…size of the room, strobe coverage concerns, and installer/AHJ preferences.
For wall mounted devices, a 15cd strobe covers a 20x20ft area, but a 110cd strobe covers a 54x54ft. there’s higher rated strobes, but typically 110cd is the highest you’ll normally find outside of an ada room or the a giant warehouse. you’ll find on most of your common strobes you can select the cd rating from 15cd up to 110cd. there’s a chart in the nfpa 72 (table 18.4.4.3.1 in the 2013 edition) that shows all of this.
so draw a 54’x54’ box and see how many it takes to cover your entire cafeteria and that’s what you’re sitting at. ceiling mounted devices have slightly less coverage, but it’s not a noticeable difference unless you’re doing a true design. since cafeteria’s are usually odd shapes, designers usually use different rated strobes on different walls to get full coverage,
corridors get special treatment, you have to have one within 15’ of each end and every 100’ in between, all 15cd. so if you only see a few in a long hallway, that’s why.