Horizontal exit question

[Sifu]

Hope this isn't too stupid. When using a horizontal exit, or any double egress door with the exit path going both ways, how would an occupant determine which way to go. For example, using a horizontal exit, the "safe" side is on one side of the now closed double egress door. Exit signs located on both sides tell people where to go, but could be leading occupants from the "safe" side, to the "unsafe" side.

 

[classicT]

One side will have alarms going off, the other wont. Typically a horizontal exit should lead to another building, i.e. separate alarm system.

 

[Sifu]

Excellent. Thanks. So what about a pair of double egress doors not associated with a horizontal exit? Any ideas?

 

[steveray]

Not necessarily a different building/ system....

1026.2 Separation. The separation between buildings or
refuge areas connected by a horizontal exit shall be provided
by a fire wall complying with Section 706; or by a fire
barrier complying with Section 707 or a horizontal assembly
complying with Section 711, or both.

 

[Sifu]

So, You could have people exiting both ways through marked exits, passing each other along the way whether it is a horizontal exit or not.. Doesn't sound ideal.

 

[ADAguy]

Sounds like a hospital or school corridor.

 

[Sifu]

Sounds like a hospital or school corridor.

This particular one is not, but the question has always bothered me. Under alarm condition the double egress doors work both ways, but how does the occupant know which way they should go? In a standard exit scenario, everyone knows to go to the stairs. Very few understand compartmentalization. I wonder if people on side #1 are running towards the exit sign on side #1, while the people on side #2 are running towards the exit sign on the opposite side of the door. In the case of a horizontal exit, each side is "protected" against the other, much like a shelter in place strategy in a hospital. In a hospital, the staff knows, they direct the residents. But what about an R2? I currently have a submittal where they are trying to use a horizontal exit, with double egress doors, because the stairs are overloaded. Makes a tiny bit of sense on paper. Then you realize that the strategy is relying on people using the horizontal exit and not the stairs, because the stairs are overloaded. Even worse, the strategy relies only some people going one way, and others going a different way, and it is counter-intuitive to normal behavior, and at the main stair, it relies on people running past it to get to a horizontal exit/double egress (because the stair is overloaded without one single occupant from the main corridor using it) , or in another location a double egress without a horizontal exit. See my post concerning the convoluted MOE for a plan.

I have a headache.

 

[steveray]

As much as I may not like it, it may not matter any more than heading to any other exit in an emergency and finding it blocked....Turn around and follow the exit signs to another exit. Nothing in most alarm systems tells the occupants where the hazard is. With voice evac it gets easier, and then hopefully the communication is clear enough to steer the occupants where not to go...

 

[Sifu]

I understand the point of view. In a horizontal exit, where both sides are following exit signs to assumed safety, and literally running past each other in the opposite direction confounds me. My experience with horizontal exits is within health care, where staff is knowledgeable and plans have been established. This is the second HE I have seen in a large R2 building, this one with a large assembly component. This is but one element of the MOE design on this project that is making me very uncomfortable. 750+ occupants on the floor in question and a very confusing MOE. Been trying to find a way to live with it but so far I just can't. To be clear, I am not claiming the HE is a code violation, just a part of the design.

 

[steveray]

Maybe we will get to the point where an addressable FA system can identify the hazard and "direct" egress a little better...That way you are not running to the stair that is on fire...Maybe shut off or change the exit sign in an impinged area? Wouldn't that be cool....Although, then I argue with myself and ask myself if this has actually created a problem anywhere...ever....Or if we are thinking about solving a problem that doesn't exist...

 

[Sifu]

I get that folks may always be running towards a blocked exit. MINIMUM code handles that with the 50% rule. My consternation is when you have the HE, with people running directly at the same doorway from opposite directions. You may be right, maybe I am a solution looking for the problem. I would add this little tidbit. In this particular case, the HE is located at a required fire wall, which is also located at a building expansion joint. In order to make all three work together they are using an NFPA 221 double 2-hr fire barrier with a vestibule. The result is two consecutive sets of double egress doors 8' apart. They are located in the center of the building (roughly) and very near the main user entry and exit stair-but that stair is not an exit from the same area as the HE. But, with the changes they made, the more I look at it, the more I think it meets MINIMUM code.