Presentation on theme: "Determining the Occupant Load"— Presentation transcript:
1 Determining the Occupant Load Occupant loads are based upon three factors:Occupancy ClassificationSquare footage of the floor or areaOccupant Load Factor
2 Existing Versus New Buildings For existing building compare the calculated occupant load with the actual occupancy in the building, take whichever occupancy is higher!For new buildings, use the calculated occupant load and design for that value
3 Occupant Load Steps Classify the Building Industrial OccupancyFind the Occupant Load FactorTable in Chapter 7 of NFPA 101Dividing the floor area assigned to that use by the occupant load factorFor determining the floor area, use the gross or net square footage as required in the codesNet square footage: Does not include areas such as restrooms, closets, and mechanical roomsThe table indicates when to use net versus gross square footage
4 Determining Capacities of Exits With the occupant load calculated, you then need to determine the widths, number, and placement of exits to ensure you can accommodate the design occupant loadFor example, if you determined the occupant load to be 1,000 people, you need to provide enough exits of sufficient widths and placement to serve 1,000 peopleDetermine what is the minimum acceptable door width
5 Calculating Capacities of Exits The capacity of an exit is determined by using:The exit widthThe exit surface (level versus stairs)In some occupancies, if there is a sprinkler system presentExample: A door has a width of 38” and the occupancy class is industrialLevel components have a capacity factor of .2Therefore, the one exit can serve up to 190 people (38”/.2)If the building has an occupant load of 1,000 people, you will need at least 6 exits (1,000/190 = 5.26)
6 Travel Distances to Exits Maximum travel distances to exits are determined by occupancy classDifferent for sprinklered and unsprinklered buildingsFor a sprinklered industrial facility, the maximum travel distance to an exit is 250 feet
7 Calculating Travel Distances Measurement of Travel Distance to ExitsThe travel distance to an exit shall be measured on the floor or other walking surface as follows:(1) Along the centerline of the natural path of travel, starting from the most remote point subject to occupancy(2) Curving around any corners or obstructions with a 12-in. clearance therefrom(3) Terminating at one of the following:Center of the doorwayOther point at which the exit beginsSmoke barrier in an existing detention and correctional occupancy as provided in Chapter 23
8 Exit Arrangements Usually, a floor must have a minimum of 2 exits Minimum number increases with occupant loadTwo exits must meet minimum separation requirementsAt least 1/3 the diagonal distance of the floor away from each other for sprinklered buildingsAt least 1/2 the diagonal distance of the floor away from each other for unsprinklered buildings
9 Exit TerminationExits shall terminate directly, at a public way or at an exterior exit discharge, unless otherwise providedThe exit discharge shall be arranged and marked to make clear the direction of egress to a public way.
10 IlluminationIllumination of means of egress shall be continuous during the time that the conditions of occupancy require that the means of egress be available for use.Artificial or natural lightingThe minimum illumination levelsFor example, floors and walking surfaces, other than new stairs, must provide at least 1 ft-candle measured at the floor
11 Emergency LightingAs required for means of egress in buildings or structures defined by the codesExit accesses requiring illumination includes only designated stairs, aisles, corridors, ramps, escEmergency illumination shall be provided for not less than 1½ hours in the event of failure of normal lightingNot less than an initial average of 1 ft-candle and, at any point, not less than 0.1 ft-candle, measured along the path of egress at floor level
12 Exit Markings, Exit Access Markings, and Directional Signage Exits, other than main exterior exit doors that obviously and clearly are identifiable as exits, shall be marked by an approved sign that is readily visible from any direction of exit access.Access to exits shall be marked by approved, readily visible signs in all cases where the exit or way to reach the exit is not readily apparent to the occupants.Directional signs with a directional indicator showing the direction of travel shall be placed in every location where the direction of travel to reach the nearest exit is not apparent.