Kurnal, thank you for your response, I apologise I may have not made the situation clear.
The gymnasium in question is not only on the escape route, it is THE escape route, so it is not in a room close to the escape route, the room actually IS the escape route. Basically, the gymnasium has been contructed in a room which used to be toilets, which were almost a sterile area, therefore posing less of a problem. The room itself is approximately 15 square metres.
To answer your questions, I'm not sure that layout of floor and number of rooms and travel distances affect my question, in basement there is only one final exit door, which is IN the gymnasium, the only other means of escape involves going upstairs to exit via ground floor.