How is the required capacity of means of egress stairways calculated based on occupant load as per Section 1005.3.1?

The required capacity of means of egress stairways is calculated by multiplying the occupant load served by the stairways by a capacity factor of 0.3 inch per occupant. Exceptions allow for a reduced factor of 0.2 inch per occupant in buildings with specific safety systems.

According to Section 1005.3.1 of the 2018 International Building Code, the capacity of means of egress stairways is determined by multiplying the occupant load served by the stairways by a capacity factor of 0.3 inch per occupant. This calculation is based on the occupant load of each story individually when stairways serve more than one story. There are exceptions for buildings other than Group H and I-2 occupancies that are equipped with an automatic sprinkler system and an emergency voice/alarm communication system, allowing the use of a reduced capacity factor of 0.2 inch per occupant. Additional exceptions apply to facilities with smoke-protected or open-air assembly seating, which may use different capacity factors specified in other sections of the code.