Fire ProtectionNFPA 101

Section 7.3.1/Capacity of Means of Egress

NFPA 101 Section 7.3.1 establishes egress capacity calculations based on occupant load and width factors for stairs, doors, and level components.

What this section requires

The capacity of each means of egress component must be sufficient for the occupant load it serves. Stairway capacity is calculated at 0.3 inches per person (or 0.2 inches for non-sprinklered buildings). Level components (doors, corridors, ramps) are calculated at 0.2 inches per person (or 0.15 inches for non-sprinklered). The total egress capacity of all exits from a floor must accommodate the total occupant load of that floor. Each exit must be sized to accommodate its proportional share of the occupant load plus any additional capacity required by the loss-of-one-exit calculation.

Why this section exists

Egress components that are too narrow for the occupant load create bottlenecks during evacuation. A 36-inch stairway serving 500 occupants would create a dangerous crush at the entrance. The capacity factors are derived from research on pedestrian flow rates through various components. The loss-of-one-exit provision ensures that even if one exit is blocked by fire, the remaining exits can handle the full occupant load. This redundancy is what makes building egress systems reliable under fire conditions.

What plan reviewers look for

Plan reviewers calculate the total occupant load per floor and verify the total exit capacity (sum of all exit widths times the capacity factor) exceeds the occupant load. They check each stairway width against its proportional share. They perform the loss-of-one-exit calculation: remove the largest exit and verify the remaining exits can still handle the total occupant load. They check door widths along the egress path.

Common violations

Exit stairway width insufficient

A 44-inch stairway serves a floor with 300 occupants but the required width based on the capacity factor is 90 inches (300 persons x 0.3 inches). Additional stairway width or additional stairways are needed.

Loss-of-one-exit not evaluated

The egress analysis shows adequate total capacity but does not check whether the remaining exits are sufficient if the largest exit is blocked. Two 44-inch stairways serving 400 occupants pass the total check but fail the loss-of-one check.

Compliance tip

Include the egress capacity calculation in the code analysis showing the occupant load, the capacity of each exit, the total capacity, and the loss-of-one-exit verification. Note the capacity factor used (sprinklered vs. non-sprinklered). Show exit widths on the floor plan at each egress component.

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Section 7.3.1/Capacity of Means of Egress

Why this section exists

What plan reviewers look for

Common violations

Related sections