It would be down to a risk assessment if you could evacuate the the number of people in the building along the fire escape route. guidance might be to use fire exit door widths.
have a look through this document it's free to download or £12 to buyhttp://www.communities.gov.uk/publicati ... afetyrisk3
How many employees are in the building and how many final exits do you have?
edit:- a width of at least 750mm can accommodate 80 people high risk , 100 medium risk and 120 lower risk. the minimum width of an escape route should not be less than 750mm. Unless it is for use by less than 5 people in that part of the premises.
On page 70 of the above document