Exit distribution

[Sifu]

I have a space with 4 exits/access doors; on the top right, there are 2 sets of double doors, a two-way dual swing double door at center right, a double door on the bottom right, and a double door at far left. The OL is handled by the far left double and the top right double/double. They show no OL for the dual swing double and the bottom right double. My question is about the distribution. '21 IBC 1005.5 mandates that a loss of any one exit access shall not result in a reduction in capacity to less than 1/2. The required exit capacity is 385. Since the 3 exits on plan right are grouped and fed by a single exit access, would this be a violation of egress distribution? In other words, if you lost the area highlighted by the red circle, you would lose access to the 3 exits on the right. If you lost the capacity of all three, the far left door would then be required to handle 1/2 the total OL. For the record, it will, but they don't show it. The way they show it with OL at only the two exit access (left and top double/double), they would have a distribution problem.

 

[steveray]

Tricky the way that is written....I don't think the intent is "losing the hallway" , but I can see how you get there...

 

[Yankee Chronicler]

The three exits at the right are not three exits, because only the double-double door at the upper right has an exit sign. The dual-swing door and the double door at the bottom are doors, but not exits.

They do show that the double doors at left will accommodate half the total occupant load. Their nomenclature indicates a pair of doors with a capacity of 340 people, to which they have assigned 128 for purposes of egress planning. 340 is obviously more than half of 385. However -- the double door at the left is either up or down a half story from the floor in question. That means converging egress has to be accounted for, so how many additional people are assigned to that exit from the other floor it serves? That might change the equation.

Why does the dual-swing door have 140 people entering through it? Is that a horizontal exit?

And why does this story have TWO open, unprotected stairs opening into/onto it?

 

[Sifu]

The dual swing is not shown with an exit sign (on this page or the E lighting page), and they assign no OL exiting through it. It is an exit from the remainder of the building on the right, with a calculated occupant load of 140. Honestly don't know why they are using a dual swing door in that location if they don't need to. The bottom door is shown with an exit sign on the electrical lighting plans, but not shown with a calculated occupant load. It exits to an egress court, which would be compliant if they needed it, but they obviously don't. There is no floor level change, but there are two stairs that come from the single floor above that are not included in the capacity for the first floor exits. Each stair has a load of 111 from above.

My puzzlement is from the language of 1005.5, which says that where access to any one exit is lost it shall not reduce the available capacity to less than 50% of the required capacity.

So lets say a fire started in the hallway at the intersection where the exit access on the right intersect (the red circle). Now access to the exits for all exits on the right side are lost. The 140 from the right turn back into the building, the load from the stair turns around and heads back up, and the load from the first floor all head to the exit on the left. All exiting is now the left side double door, and that door can handle the load.

I think this meets code with the capacity of the far left door being 340, which is more than 1/2 the required capacity. Just analyzing this to make sure I understand the loss of "access to one exit" language, since this appears to be a loss of access to more than one exit.

They way they are somewhat inconsistent with the way they depict it doesn't help. If the dual swing is not an exit from the are in question, why is dual swing?? If they don't need the bottom door to be an exit, why does it have an exit sign on the E page??

This an exercise in increasing my understanding of the code, and of how it applies here because I can't recall a situation like this before.

 

[steveray]

I think this meets code with the capacity of the far left door being 340, which is more than 1/2 the required capacity.

I agree....