Industrial Unit Exit

[Guest Toby]

Hi all, 

I have an industrial unit divided into two by an OSB wall with one side still in use a mechanical workshop with the other hoping to be an events space. The events space side has it's own roller shutter door with a single exit through it so only allowing for 60 persons which isn't enough.  How would the occupancy be calculated if the shutter was up leaving the front of the unit completely open while the event was taking place? I guess the alternative is to rebuild the dividing wall with 30 min protection and use the second exit in the workshop? 

[Guest Toby]

Here's a sketch of the unit. 

[AnthonyB]

Or put a new second final exit in the outer wall of the event space unit? Evacuating a public place of assembly through a workshop area is a non starter.