Section 7.3.2/Capacity of Means of Egress
NFPA 101 Section 7.3 establishes the method for calculating required egress width based on occupant load using per-person width factors for stairs, level components, and ramps.
The required egress capacity (width) is calculated by multiplying the occupant load by the per-person width factor. For stairways, the width factor is 0.3 inches per person for buildings without sprinklers and 0.2 inches per person for buildings with sprinklers per Section 7.3.3.1. For level components and ramps, the factor is 0.2 inches per person without sprinklers and 0.15 inches per person with sprinklers. The minimum clear width must not be less than 44 inches for stairways and exit access serving 50 or more occupants, or 36 inches for stairways and exit access serving fewer than 50. Door openings must provide at least 32 inches of clear width. The required capacity must be maintained throughout the entire length of the egress component. Where egress components merge (two corridors joining at a point), the downstream component must have a capacity equal to or greater than the sum of the merging components. The egress capacity works together with the IBC egress width calculations and the means of egress arrangement requirements.
Why this section exists
Egress capacity determines whether the exit paths are wide enough to allow all occupants to evacuate within an acceptable time. Too-narrow stairs, corridors, or doors create bottlenecks that slow evacuation and can cause crowd crush in emergencies. The per-person width factors are derived from pedestrian flow research measuring the effective width (clear width minus boundary layer) needed for a given flow rate. The sprinklered reduction reflects the extended evacuation time available when sprinklers control the fire. The factors are intentionally different for stairs (slower movement, higher risk of falls) versus level components (faster movement).
What plan reviewers look for
Plan reviewers calculate the occupant load for each floor and multiply by the appropriate width factor to determine the required egress width. They verify each stairway, corridor, and exit door provides the required clear width. They check that the width is maintained throughout (no pinch points from handrails, doors, or equipment). They verify the width factor used (sprinklered vs. unsprinklered, stairs vs. level). For merging egress paths, they check that the downstream width accommodates the combined occupant loads. They check the minimum widths (44 inches for 50+ occupants, 36 inches for fewer than 50) are met even when the calculated width is less.