Q.
What do you mean by "Common Path of Egress Travel"?
A.
The common path of egress travel, or CPET, is defined in the IBC as:
"That portion of exit access which the occupants are required to traverse before two separate and distinct paths of egress travel to two exits are available. Paths that merge are common paths of travel. Common paths of egress travel shall be included within the permitted travel distance."
In other words, when occupants are restricted to one path before they have a choice of going in two directions to reach separate exits, that one path is the CPET (See Figure 5). In all occupancies, except for Groups H-1, H-2, H-3, and I-3, the CPET is limited to 75 feet. For Groups H-1, H-2, and H-3 occupancies, it is limited to 25 feet, and for Group I-3 it is limited to 100 feet.
There are two exceptions that allow the CPET to be extended.
One exception allows the CPET to be 100 feet in Groups B, F, and S if the buildings are sprinklered throughout.
The second exception allows the CPET to be 100 feet in tenant spaces of Groups B, S, and U when the occupant load is 30 or less.
As stated in the last part of the definition, the CPET is included within the permitted travel distance and is measured using the same principles. For example, a nonsprinklered Group B building is allowed 100 feet of travel distance per Table 1016.1. Within that distance, 75 feet is permitted to be a common path of egress travel.
Ref:
Ronald L. Geren (2009) Travel Distance. The Code Corner No.29. Available at
http://www.specsandcodes.com/articles/code_corner/The%20Code%20Corner%20No.%2029%20-%20Travel%20Distance.pdf