Why this is an egress capacity calculator
US building and fire codes do not require controlled descent devices, escape chutes or similar rescue equipment in normal occupancies. Life safety is achieved instead by providing enough independent exits, enough egress width and short enough travel distance, so there is no legal quantity table for descent devices to calculate. This tool therefore checks the egress provisions the IBC actually requires for a floor.
Occupant load comes from the floor area divided by the occupant load factor in IBC Table 1004.5. The minimum number of exits follows IBC 1006.3: two exits up to 500 occupants, three from 501 to 1,000 and four above 1,000. Egress width uses IBC 1005.3, which is 0.3 inch per occupant for stairways and 0.2 inch for other components, reduced to 0.2 and 0.15 inch where the building is sprinklered and has an emergency voice alarm system. Absolute minimums of 44 inch stairs, 36 inch where the occupant load is under 50, and 32 inch clear door width also apply.
Travel distance limits come from IBC Table 1017.2 and depend on occupancy and sprinkler protection, commonly 200 ft unsprinklered and 250 to 300 ft sprinklered, so the limit is entered rather than assumed. Common path of egress travel, dead-end corridors, exit separation distance and stair discharge also have to be checked. Have the design reviewed by the architect of record and the AHJ.
Frequently asked questions
They are not credited as a required means of egress in the IBC or NFPA 101. Some owners add them as supplementary equipment, but they cannot reduce the number of exits, the egress width or the travel distance the code requires.
Single exit spaces are allowed only within the limits of IBC Table 1006.2.1 and the single-exit story provisions, which cap occupant load and common path of travel. Outside those limits two separated exits are required.