When a fire occurs within a building, it is vital that the occupants have an easily accessible egress point. These exits are strictly regulated, in every aspect, by the building code. The location, size and fire protection of the exit is vital to assuring people are able to get out of the building to safety. Calculating the capacity of a current exit is done by measuring its width and doing a calculation to understand how many occupants it can serve.
Walk along the egress path and determine the narrowest location in the route. You may need to measure various areas with the measuring tape if it is not obvious. It is common for the exit door to be the narrowest point.
Measure the narrowest point in this location for its width in inches.
Determine if the egress path has a set of stairs that must be used during the exit. If it does, divide the width by three then multiply the result by 10. The result is the number of occupants the exit can serve.
Divide the width by two then multiply the result by 10, if the egress route has no staircase. The result is the number of people the exit can serve for egress purposes.