When the tool is run the compartment area is not added and still shows 0. 

Solution: For the tool to work, there are two things that need to be entered into the spaces.

Firstly: the spaces need to have the same Fire_CompartmentationReference value. This is the value to identify which spaces are in the same compartment.

Secondly: Fire_OccupantLoadFactor needs to have a value over 0m², change the value to 1 and run the tool again.