Occupancy signs

Factual Questions
1

Today while I was out on lunch and standing in line I took note of the sign above the door (on the inside) which read OCCUPANCY 150. My estimated nose count at the time was about 50-60 people (including the workers and other people in line) and about half the tables were occupied. I have seen these signs in public buildings, usually in restaurants. What I am wondering is, what purpose does this serve? I believe that it has to do with the maximum number of people who can be in the building at once so that they can safely evacuate it in the event of a fire, earthquake or other emergency. This brought to mind several questions:

(1) How is the maximum occupancy determined? Is there some formula that is used based on square footage, number of exits (including emergency exits), accessibility to the exits, types of doors (single vs. double doors), etc.?

(2) If the building were occupied beyond its capacity, who would be there to determine that it is beyond capacity? Having once worked as a manager in fast food in another life, I know damn well that if the place were this busy, the last thing anyone has time for is to count the number of people in the building.

(3) In the event of an emergency such as a fire, if people died as a result of the emergency, how would investigators use this number (assuming that it is kept on file by public safety officials)? If they determined that the building was beyond its capacity at the time of the incident, would there be liability issues? Whose responsibility would it be?

2

Table 10-A of the Uniform Building Code is generally (I believe) used to determine maximum occupancy. There is not one equation used for all building types.

You can see the kind of variation here (http://www.sandiego.gov/development-services/industry/pdf/bnl10-01.pdf). I don’t think the UCB is available online anywhere.

DISCLAIMER: This is just the result of research, not any first hand knowledge. I may be completely wrong.

3

You could go to any public library and get a copy of the UBC (Uniform Building Code) and the UFC (Uniform Fire Code) and try to figure out the maximum occupancy.

I assume that fire inspectors and building code inspectors make the final determination as to what goes on the sign.

In Los Angeles, fire inspectors are VERY picky about overcrowding. They’re picky about everything when it gets right down to it. (Nobody hangs up banners at Dodger games because they are against fire regulations.)

4

The UBC is a decent resource, but the general end-all for occupancy determination is NFPA 101, the Life Safety Code ®. This standard is devised by the National Fire Protection Association, and approved by its membership (of which I am one) at an annual meeting. NFPA 101 is on a 3 year revision schedule, the most recent edition being released in 2000. Most states that have adopted this Code as law are currently using the 1997 edition.

Per The 1997 edition (I don’t have the 2000 edition at home), the section regarding existing assembly occupancies (assembly = “building or portion of a building holding > 50 people for such purposes as deliberation, worship, entertainment, eating, drinking, amusement, or awaiting transportation”) there are two main factors regarding occupant loading: floor area and the means of egress.

Floor area calculations for assembly occupancies such as restruants and dining/drinking areas is based on the net square footage of that area, so we’re subtracting the areas taken up by tables, benches, walls, etc. Each person in the space is allowed to have 15 square feet. So, if you measure out the whole space of the dining area and its 2000 square feet with 500 sq’ taken up by columns, tables, walls, etc, you have 1500 square feet for occupancy. Since each person gets 15 sq’, you are allowed 100 people in that space. There are different load factors for different occupancies.

If you have fixed seats, such as those in an auditorium, the occupant load is the number of seats. There are all sorts of rules for how many seats you can have and where your exits have to be for those seats.

The means of egress calculations takes into account the width and number of doors and exits (exit meaning the entire pathway leading from your seat to the outside, not necessarily the door with the “exit” sign above it). There are minimum standards that must be met, but going above them can increase the number of people that can be allowed into that space.

The problem arises when the space has exits for fewer people than the floor area calculation says you can hold. If that happens, then the lower number (exit or floor area calc) is the maximum allowed occupancy. If you have a space that has tons of code compliant exits, some “authorities having jurisdiction” (codespeak for the person(s) enforcing the Code) may allow, at their discretion, an increase in the maximum occupancy. Don’t, however, come to me to get the local fire inspector to let you have more people in your resturant. Whatever he/she says is what goes wherever you are.