Where Should Exits be Located?
CODE & STANDARD REFERENCES
Where should exits be located?
So far in this series, we’ve covered exits, types of exits, the different segments of exit access, exits and exit discharge, and in our last segment, we talked about arranging exits so that they’re far enough apart from each other.
In this segment, let’s talk specifically about where the exits need to be located.
Exits should be sufficiently separated so that a fire would not render both exits unusable. Ideally, exits should be located near the exterior of the building. And exits should be designed so they are readily available to all building occupants. Finally, they should be arranged so that an occupant doesn’t have to travel too far to reach them. Let’s dive in.
HOW MUCH SEPARATION?
This “sufficiently separated” concept sounds awfully familiar. It sure is. In the previous video, we talked about exit access doors. Specifically, we were looking at large rooms or a suite of rooms. Because those rooms have 50 or more occupants, there must be two ways out (two exit access doors). These two ways out must be far enough apart so that a fire wouldn’t block both doors.
This minimum separation distance is one-half the diagonal of the room in nonsprinklered buildings and one-third the diagonal in fully sprinklered buildings. The same concept also applies to exits.
Let’s imagine a multistory building with two interior exit stairs near the core of the building.
Around the perimeter of the building are various office tenants.
The only way out of the building is through one of these interior exit stairs.
Now, to maximize leasable space, the developer wants the core to be as small as possible.
This means bringing the stairs closer together. So if a fire were to occur in one of the tenant spaces, both exit stairs would be available.
But what if the fire occurred in the core?
Could it create a situation where both exits are blocked? What minimum distance must the two stairs be separated by? In this case, it is one half the diagonal of the building.
Just like exit access, in a fully sprinklered this is reduced to one-third the diagonal of the building.
WHY LOCATE EXITS NEAR EXTERIOR?
Why should interior exit stairs ideally be located near the exterior of the building?
Well for one, it makes the one-half or one-third diagonal exit separation easier.
The other reason is because of exit discharge. If you recall, we said as soon as an occupant enters the interior exit stair, they have exited the building.
From a life safety perspective, this is true but from a literal or intuitive standpoint, they are still in the physical structure that we call a building. Eventually, the stair will discharge the occupant somewhere. Either the stair will discharge the occupant directly to the outside or they will discharge the occupant back into the building.
Which is safer? Well, directly outside.
The building is on fire, after all. But that would mean the stairs have to be located along the exterior wall.
Because requiring all interior exit stairs to discharge directly to the exterior is restrictive from a design perspective, the code permits up to 50% of interior exit stairs to discharge back into the building, provided several requirements are met.
We’ll dive into this in much greater detail in a later video. The takeaway is that locating interior exit stairs on exterior walls is ideal, where feasible, due to exit separation and discharge requirements.
AVAILABILITY TO OCCUPANTS
Exits also must be available to all occupants.
What does available mean? It means the occupant has access to the exit.
If there is no pathway, then the occupant cannot reach the exit.
If the pathway has doors that are locked or under control of another tenant, then these exits are not available.
This goes hand in hand with the concept of exit access that we discussed in the previous video. It’s a bit of chicken and egg, but typically the exits are set first and the exit access is designed around it. But…there are situations where additional exits must be added late in design.
One example might be a public lobby of an otherwise secure building. It has only one set of doors for entry and exit. Occupants are not permitted to go beyond the building lobby without proper security credentials, even in an emergency.
So, this means that for occupants in the lobby, there is a single exit.
But if this lobby has more than 50 occupants, two exit access doors (or two exits in this example) are required, meaning a second exit would have to be added.
DISTANCE TO EXITS
Finally, exits should be located so that occupants don’t have to travel too far to get to them.
If we assume the building is on fire, then every second counts in an evacuation. The further away the exit is, the longer it will take for an occupant to get out. So, how far is too far? What is the maximum travel distance?
We’ll dive into measurement of travel distance to exits in later videos. It depends on occupancy but generally, the range is between 100 feet to 400 feet for the maximum distance an occupant is permitted to travel before reaching the nearest exit.
So, how should exits be located?
They should be located far enough apart from each other, so that a fire would not render both exits unusable. Ideally, exits are located near the exterior of the building.
Exits should be readily accessible to all buildings occupants. And the distance an occupant has to travel to reach an exit shouldn’t be excessive.
We’re going to get through some examples on exit arrangement in the next segment and get some practice working through those.
From there, we’re going to cover how we help occupants know where exits are located.
I’m Steven Barrett, this is MeyerFire University.
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