From NFPA Fire Protection Handbook Section 4, Occupant Load: "Occupant load, or the number of people to be expected in a building or an area within a building at any time for whom exits must be provided, is determined by the actual anticipated occupant load but not less than that number obtained by dividing the gross area of the story or the net area of a specific portion of the building by the area in ft^2 projected for each person." That projected area for each person is the occupant load factor, and it should be divided into the net, say class room, area that correlates with that load factor. The quotients from all net occupied areas are summed to determine the Occupant load for that floor. In your case, if you wanted to account for people waiting to get into classes before the lecture period, you would apply a safety factor to that sum. But, before doing so I would consider whether that condition applies to the normal state of occupancy for the premises. I would suspect that it does not.
Consider a single story elementary or high school. All of the students enter the corridors between classes, but they all end up in classrooms (or smoking cigarettes in the bathroom) when the next lecture session begins. The occupant load doesn't change for the floor throughout the day.
I use the business factor of 100 sqft/person. Bathrooms, offices, circulation spaces, I use 100 for all of them.
It may be a little overkill, but schools frequently have events where parents and students show up at the same time. This gives a margin for error if your egress calculations are tight.
I am juggling several hats as our university's new facilities manager, safety/risk manager, etc., but am having a conundrum of sorts. Like all universities, we get annually "graded" on space utilization-- how efficiently are we using the space we have. One of the components is Percent Capacity, which is simply a ratio of students per room capacity (i.e. desks/seats in a classroom). For some reason we have our heads stuck on this concept that we MUST use the maximum occupancy from life safety calculations, and I'm trying to tell folks that we can determine our own capacities based on optimal learning environment. But this is another topic for another venue.
My question is this: Can I determine a room capacity for a classroom or lab by just walking in and measuring the room's square footage and using a load factor? Some of our classrooms have so many desks it looks like a cattle car going to slaughter. I'd like to be able to go room to room and say, "This is the maximum allowable seats...". Appreciate any simple tips for a simple guy. Thanks. Ron
Hi Ron! Appreciate the question. I've summarized and posted it here for daily discussion: https://www.meyerfire.com/daily/determine-existing-classroom-occupant-load
Check the definitions for net vs. gross area, these will help clarify:
(NFPA 101; 2018)
22.214.171.124.1 - Gross, includes corridors, closets, etc.
126.96.36.199.2 - Net Floor Area, doesn't include corridors, etc.
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