Emergency exits, or egress routes as many may know them by, have set clearance requirements to ensure building occupants have enough space to safely exit the building. The following dimensions help with creating a consistent environment for employees and have been proven to assist in meeting the most optimal emergency evacuation needs.
What is egress?
Egress capacity is based on the width of the component and the type of occupancy. According to the NFPA, the most common capacity feet factor for stairs is 0.3 inches per person and all other modes of egress such as ramps and level areas are 0.2 inchers per person.
Egress width requires that a door must be at least 32 inches in width to allow for the passage of wheelchairs. However, that number can be reduced to 28 if the room is less than 70 square feet. The maximum width of an emergency evacuation door is 48 inches.
Corridors at a minimum should be 36 inches wide for new buildings and 28 inches for already existing buildings. The ceiling should be at least 7.5 feet tall.
Egress routes such as stairs must have a pathway of at least 44 inches to allow for two people to descend side by side comfortably. The NFPA mentions a minimum 11-inch tread and a maximum of 78-inch risers for new stairs. Landings are needed every 12 feet of height and the dimensions of tread and risers should not exceed 3/16th of an inch and 3/8ths of an inch respectively. Any stairs that are more than 30 inches from the floor must provide handrails that are no more than 37 inches and no less than 30 inches from the stair treads. Guards must be at least 42 inches tall and prevent a 4-inch sphere from passing through the rails.
As for ramps, the NFPA code allows for a 1-in-12 slope for a 6-inch or greater rise. Steeper yet shorter ramps are allowed but the single rise for a ramp is restricted to 30 inches. These are also in need of guards and handrails with the same specifications as stairways.
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