Determining the maximum occupancy level of buildings is the responsibility of a local fire authority. The National Fire Protection Association Life Safety Code is often used as the standard to calculate occupancy levels of buildings allowing safe exit in the event of an emergency.
Life Safety Code
The Life Safety Code was introduced following the Triangle Shirtwaist Fire of 1911, according to the John Jay College of Criminal Justice. The code is updated by the NFPA every three years with local governments determining which published version of the Life Safety Code is applicable.
To begin calculating the maximum occupancy level of a building, its use must be determined. Use groups of buildings include educational, assembly and recreational. Occupancy levels can be calculated using square footage, with NFPA standards allowing five square feet of space per person apart from waiting areas, where three square feet per person are allowed.
The number of exits can also be used to determine the maximum number of people allowed in a building. Buildings with generally less than 500 occupants are required to have two available exits, 500 to 1,000 occupants require at least three exits and over 1,000 occupants require at least four exits for emergency evacuations. The exits should be located as remotely from each other as possible.