...
If the room consists of luminaire group(s) and/or tubes and some of these are to be used for emergency lighting, you have to split these first.
Select the luminaire group, and choose "Split group" from the context menu.If the emergency luminaries are of a specific type you have to insert some of these first.
...
Press the emergency button on the left toolbar. The editor toolbars and buttons will be changed to emergency mode.
While the emergency mode is active, only changes to the emergency luminaires and working planes are allowed.
Next, activate a luminaire that is suitable for emergency light by clicking at it.
From the object properties menu, check the Emg.light checkbox:
...