What Does Occupant Load Affect?

MeyerFire University | LS182.04

By Steven Barrett, PE

RESOURCES

• One-Page Summary [PDF]
• Notes Page [PDF]

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TRANSCRIPT

What Does Occupant Load Affect? 

INTRODUCTION

So far in this series we’ve talked about what occupant loads are, how to calculate them, and how to use occupant load factors.  

But who cares? 

That’s what we’re going to cover today. So, I calculated my occupant loads. What do I do with this information? What happens if I calculate a high occupant load for a room or floor of a building? Does it really matter? Of course, that’s why we’re here. Let’s get started.

#1 NUMBER OF EXITS

The calculated occupant load will determine the minimum number of exits required per story of a building. We’ll dive much deeper into this in a future video, but the basic idea is more occupants means more exits are required. If a building’s use changes which results in a large increase in occupants, it could mean that the building does not have enough exits to accommodate these occupants in an emergency. Meaning the change would not be permitted unless more exits are added (which is very difficult to do in an existing building) or the function of the building is changed so that it results in fewer calculated occupants. 

#2 NUMBER OF EXIT ACCESS DOORDS

Generally, rooms with 50 or more occupants require two exit access doors. The general premise of egress is that there are always two ways to get out. While this is generally true, rooms or spaces with 49 or fewer occupants are permitted to have a single way out. But when there are 50 or more, the space is required to have two ways out, in case one of the exit doors was blocked by fire or other emergency. Like all of these topics, we’ll dive deeper into this in later videos. The takeaway is that occupant load affects number of exit access doors.  

#3 DOOR SWING

Similarly, when serving an occupant load of 50 or more, doors must swing in the direction of egress. Meaning, the path from the room until the occupant is outside of the building, all doors must swing in the direction of egress – towards the exit.  

#4 SPRINKLER SYSTEM

The number of occupants could determine whether or not a building requires an automatic sprinkler system. For some occupancies, if a certain number of occupants are present, then an automatic sprinkler system must be provided. For example, in Assembly A-3 occupancies, if there are more than 300 occupants per fire area, then an automatic sprinkler system must be provided at the building.

#5 FIRE ALARM & VOICE EVACUATION SYSTEM

Similar to sprinklers, the requirements for whether a fire alarm system or even an emergency voice alarm communication type system must be installed in the building are both affected by the number of occupants. Similar to the previous example, in Assembly occupancies with more than 300 occupants, a fire alarm system is required to be installed. In assembly occupancies with more than 1,000 occupants, an emergency voice alarm communication system is required to be installed.  

#6 PLUMBING FIXTURES

The number of occupants is used to determine the minimum number of plumbing fixtures required. More people means more toilets. The exact procedure will be covered elsewhere but like the previous example, if a building is renovated to increase the number of occupants, it could mean that more toilets need to be added to accommodate those additional people.  

#7 STRUCTURAL/SEISMIC DESIGN

The number of occupants affects the Seismic Risk Category. For example, an assembly occupancy is a Rick Category II but when 300 or more occupants are present, this goes to Risk Category III. Similarly, other occupancies have occupant load thresholds where a higher Risk Category is required.  

#8 OCCUPANCY
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We’ll cover this in great depth in the next video, but the number of occupants affects the occupancy classification. When an area used for gathering is fewer than 50 occupants, it is classified as a Business occupancy but 50 or more occupants, it is classified as an Assembly occupancy.

SUMMARY

What does occupant load affect? 

A lot. It validates that the means of egress system, specifically the number and arrangement of exits and exit access doors. It determines whether certain fire protection systems (like sprinklers or fire alarm) are required in the building. It determines the minimum number of plumbing fixtures (usually). It affects structural/seismic design. It can also affect occupancy. 

In our next segment we’ll discuss the difference between occupant load factors and occupancy, because this is a concept that often gets confused.  

I’m Steven Barrett, this is MeyerFire University.