Occupancy / Exit Widths

[Midland Retty]

HI All

Wonder if you can help - as usual this one of those questions that really I should know but has confuddled me a little

Mr Bloggs want to open a nightclub - with a capacity of 400 people. Floor space will take this no problem

He wants to achieve his occupancy this with just two final exit doors.

Both doors would have to be capable of taking 400 people - I have no problem with the theory behind how exit widths work and ordinarily this wouldnt present an issue etc

Trouble is that all guidance stops at 1800mm wide doors allowing a max of around 360 / 370 persons on each door

Can you continue extrapolating beyond 1800mm or is the limit set on a max of 1800mm doors?

The only thing I could think of was that any doors larger than 1800 would become to unweildy to open perhaps hence why the guides stop at that width?

I wont bore you with the reasons behind why heh only wnats two final exit doors, so lets just forget that issue for the time being - id be grateful of you thoughts and comments as always

[kurnal]

Its not the width of the door leaf that matters for calculating the exit capacity- its the width of the opening. Door leaves of 1100mm are common place- so two together would not be a problem. Theres no limit on the width of a door leaf but as you say too big and they become too heavy to hang on conventional hinges.
The other thing about conventional guidance is that it is all calculated on an evacuation time of 2.5 minutes and other factors may allow this to be flexible- in accordance with DD9999/ BS9999

[Midland Retty]

Its not the width of the door leaf that matters for calculating the exit capacity- its the width of the opening. Door leaves of 1100mm are common place- so two together would not be a problem. Theres no limit on the width of a door leaf but as you say too big and they become too heavy to hang on conventional hinges.
The other thing about conventional guidance is that it is all calculated on an evacuation time of 2.5 minutes and other factors may allow this to be flexible- in accordance with DD9999/ BS9999

Hi Prof

Yes you're right and thats what I meant - available widths as opposed to door widths!

Anyway thanks for that - it puts my mind at rest!

[nearlythere]

The only thing I could think of was that any doors larger than 1800 would become to unweildy to open perhaps hence why the guides stop at that width?

BS5588 Pt6 does not stop at 1800mm. Table 4 — Capacities of exits and escape routes

Maximum number of persons          Width mm
                                                               
50                                                 800
110                                               900
220                                               1100
240                                               1200
260                                               1300
280                                               1400
300                                               1500
320                                               1600
340                                               1700
360                                               1800

NOTE Capacities of other widths exceeding 1 100 mm may be obtained by linear interpolation or extrapolation.

Therefore 400 persons can use a 2000mm doorway.

[Midland Retty]

The only thing I could think of was that any doors larger than 1800 would become to unweildy to open perhaps hence why the guides stop at that width?

BS5588 Pt6 does not stop at 1800mm. Table 4 — Capacities of exits and escape routes

Maximum number of persons          Width mm
                                                               
50                                                 800
110                                               900
220                                               1100
240                                               1200
260                                               1300
280                                               1400
300                                               1500
320                                               1600
340                                               1700
360                                               1800

NOTE Capacities of other widths exceeding 1 100 mm may be obtained by linear interpolation or extrapolation.

Therefore 400 persons can use a 2000mm doorway.

Cheers Nearlythere

Its what we thought - just wanted confirmation- the suns out down here you see and as a result our office gets warm and it affects our out brains


We're all off to the pub now to cool down and deliberate why we ever agreed to go into fire safety in the first place.

[Dragonmaster]

I seem to remember something i was told about human behaviour. Any opening larger than 4 exit widths would be well populated during evacuation around the sides of the opening, but the larger middle portion would be less so (widths are calculated using an overlap i.e. people don't move shoulder to shoulder but squash towards each other), similar to the restrictions placed on staircases that need intermediate handrails over a certain width. I can't recall the exact reasoning, and i can't locate any written script.

Could Mr Bloggs provide 5 exit widths made up of a two leaf and three leaf wide opening

[nearlythere]

I seem to remember something i was told about human behaviour. Any opening larger than 4 exit widths would be well populated during evacuation around the sides of the opening, but the larger middle portion would be less so (widths are calculated using an overlap i.e. people don't move shoulder to shoulder but squash towards each other), similar to the restrictions placed on staircases that need intermediate handrails over a certain width. I can't recall the exact reasoning, and i can't locate any written script.

Could Mr Bloggs provide 5 exit widths made up of a two leaf and three leaf wide opening

Maybe a little like pressure loss due to friction in a hose. Laminar and Turbulent Flows.

[jokar]

ADB B1 will give you the same result if you extrapolate the table, or you could look at the LDSA Technical Guide for Ents premises and look at table C.

[Izan FSO]

I seem to remember something i was told about human behaviour. Any opening larger than 4 exit widths would be well populated during evacuation around the sides of the opening, but the larger middle portion would be less so (widths are calculated using an overlap i.e. people don't move shoulder to shoulder but squash towards each other), similar to the restrictions placed on staircases that need intermediate handrails over a certain width. I can't recall the exact reasoning, and i can't locate any written script.

Could Mr Bloggs provide 5 exit widths made up of a two leaf and three leaf wide opening

If he did then the largest exit would have to be discounted and you are back to square one. if there are only two exits in the premises they should both be the same size and allow escape of all ocupants through the one door not affected by fire

[Dragonmaster]

What i meant is to retain the two exits (presumably front and back) each made up of 5 exit widths each consisting of a double leaf and separate triple leaf next to each other. By discounting one 'exit', you're still left with 5 exit widths at the opposite end of the premises.