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Calculate occupancy

Guest Craig

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I’m trying to calculate occupancy for a 4 storey building. There’s 2 escape routes, both protected stairwells. All rooms on each floor are used for either office space or function rooms. We are restricted with occupancy due to the size of the exit doors, both protected stairwells have fire exit doors of 750mm that lead into the stairwell and this is the same from the 1st floor to the 4th floor with the ground floor having a fire exit door of 1050mm, this is the final exit. 


Am I right in thinking that each floor occupancy is restricted to 100 people (normal risk) due to having to take off 1 exit for a fire situation? Also are we then restricted to 200 people for the total building due to only having final fire exit doors of 1050mm, or can we count both final fire exit doors giving us a total of 400 people? 


I hope this makes sense! 



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I am assuming you are using the DCLG guide for offices and shops.

The travel distances are based on an arbitrary time, accepted by most as 2.5 minutes and in that time 200 will have reached safety, allowing others to fill the staircase which provides 30 minutes of comparative safety. So it all depends on the capacity of the staircase, which if it is two hundred persons then as first stair full reaches safety the remainder will be filling the staircase, so they will all be in the staircase, a place of comparative safety within approx 2.5 minutes.

So you need to consider the capacity of the staircase and if it falls short then you may have to consider a two stage alarm.   

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