Escape routes, travel distances and occupancy capacity
Three numbers do most of the work in a commercial assessment. Travel distance is how far someone must walk to reach a place of relative safety — broadly up to 18 metres where escape is possible in only one direction, and up to 45 metres where there is a choice of routes, varying with risk category. Exit capacity is how many people a given exit width can discharge, calculated from door widths and staircase widths. Occupancy capacity is the resulting maximum number of people the premises can safely hold, and in licensed premises it is frequently a condition of the licence. Assessments fail most often not because exits are missing but because a fit-out has extended travel distances or an exit has been narrowed or obstructed since the layout was designed.