What is an "Occupant Load"?
What is an “Occupant Load?”
This is the start of a new series covering “Occupant Loads”.
What is an “occupant load?” How do we determine occupant loads? What is an occupant load factor? What is the occupant load used for and what parts of building design does it affect? What’s the difference between “occupant load factor” and “occupancy”?
Let’s start at the beginning. What is “occupant load”?
DEFINING THE NUMBER OF PEOPLE
Simply, it’s the number of people in a room or space. Imagine a concert venue, sold out show, the band is getting ready to come on, and people are just piled in, body to body, to see the show. That’s an example of a high occupant load – a whole lot of people. By contrast, a warehouse is an enormous building with lots of storage but very few people, typically.
What’s occupant load?
More specifically, it’s the maximum number of people in a room or space. So, if you are sitting in your office right now, you might be the only person in there (plus maybe the occasional faithful pet). So that’s an occupant load of 1, right?
But I said maximum, didn’t I? We could definitely cram more than 1 person in a small office, you could probably get 10 if they all stood should to shoulder. Well, yes, that’s possible but that’s not how an office is intended to be used.
A better definition is the maximum probable number of occupants in a room or space, consistent with its intended function. Now we’re getting somewhere.
So, it’s the number of people in an office when it’s being used like an office is typically used – a desk and a chair for focused individual work, maybe light storage, only one occupant, generally. It’s an office when it's being used like an office.
It’s a warehouse when it’s being used like a warehouse – lots of storage with very few people. It’s a concert venue when it’s being used like one, with loads of people.
Okay, but why maximum? Why not average or typical?
In history, when fires have tragically taken lives of many, these have often occurred when the buildings are at their maximum occupancy.
The greatest risk of injury or death from fire is when buildings are at maximum occupancy, because there are more people are potentially in danger if a fire were to occur.
Another less obvious reason is because the people themselves block and prevent access to exits, especially in situations of panic. This is why codes generally require that all rooms be considered occupied simultaneously, at their maximum probable number of occupants, to establish the total occupant load of building.
JUST COUNT THE PEOPLE?
So, we just count the number of people?
Not exactly. Remember, this is a design concept, so the building isn’t built yet. It’s not even fully designed yet, so we can’t just count people. You could look at the furniture plan and count seats but furniture is moveable (and removeable) and furniture can be modified or added, so that isn’t really the best metric.
OK, so you’ve explained a lot of ways how not to do it, how do you calculate occupant loads?
I thought you’d never ask. We’ll cover that in the next video.
What is “occupant load”?
It is the maximum probable number of occupants in a room or space, consistent with its intended function. It represents in a worst-case yet realistic scenario the total number of people that could be in a room, a floor, or the entire building. It is a design concept that is used to determine minimum safety features and affects many portions of building design and life safety (which we’ll go through in a later video).
I’m Steven Barrett, this is MeyerFire University.
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