Why occupancy permits are required
Buildings are designed for specific purposes, and safety requirements depend on how those spaces are used. When a building or part of it changes from its original use, the safety codes that apply often change too.
For example, if a space built as an office is converted into a retail store, the number of combustible materials (like products and packaging) usually increases. This raises the fire risk, which may mean the existing sprinkler system is no longer sufficient. More people in the space can also mean more exit doors are needed so everyone can evacuate quickly in an emergency. Shelving can create obstacles, and higher occupancy often requires additional washrooms.
Certain business activities may also need special ventilation to keep the air safe, or alarm systems to provide faster fire warnings. Some types of businesses must have sprinklers and alarms, while others in the same building may not.
In short: when the use of a space changes, safety requirements change too—to keep everyone safe.