Means of Egress: Load, Width, Distance, and Components
This domain covers the continuous path from any point in a building to the public way. Expect calculation items: occupant load, required egress width, number of exits, and travel distance. The exam rewards clean arithmetic and punishes mixing net and gross area factors.
Core rules
- Occupant load is computed from the floor area and the use-based factor (business is commonly 150 gross square feet per occupant; assembly concentrated uses are computed from actual seats). Where fixed seats exist, count the seats.
- Every space has three egress components: exit access (the path to the exit), the exit itself, and the exit discharge to the public way.
- Required width is generally 0.2 inch per occupant for level components and doors, and 0.3 inch per occupant for stairs. Where the building is sprinklered and has an emergency voice/alarm communication system, those values may be reduced to 0.15 and 0.2 inch respectively.
- Two exits are required once the occupant load reaches 50 in most occupancies, with additional exits as the load grows.
- Travel distance and common path of egress travel are separate limits, and both are measured along the actual walking path.
Worked example
A 7,500-square-foot business occupancy: 7,500 / 150 = 50 occupants. Because the load reaches 50, two exits are required. Door width: 50 × 0.2 = 10 inches total, easily satisfied by two 36-inch doors at 32-inch clear width - but the 50-occupant trigger, not the width math, is what governs the layout. Stair width: 50 × 0.3 = 15 inches, so the minimum stair width rule, not the calculation, controls.
Traps
- Using net rather than gross floor area, or deducting storage rooms that still count.
- Applying the reduced width factors without confirming both the sprinkler and the voice/alarm conditions.
- Confusing exit sign requirements with exit illumination requirements.