9999 interpretation

[lyledunn]

Would one of you kind experts help me interpret 17.7.3 on page 71 of BS9999? The last paragraph would seem to imply that a room with only one exit to a corridor which provides escape in two directions  can be treated as a room with alternative exits providing the travel distance requirements are met. My reading of this would be, all else considered, that such a room could accommodate the number of people that the single exit door to the corridor would dictate. Thus if the door allowed, a room which might ordinarily be restricted to 60 can be significantly increased??

[Mike Buckley]

No, the essential part of the wording is 'there may only be one exit from a room to a corridor, from which point escape is possible in two directions'. The escape in two directions starts at the exit to the room, hence the room has only one exit and the travel distance etc. inside the room is in line with the escape in one direction only when they reach the door the travel distance then expands to escape in more than one direction and the occupancy of the room should be for a room with only one exit.

[lyledunn]

So at what point could the room be considered to have alternative exits? Consider a room with a door to a corridor from which escape is available left and right through final exit doors. Say if the door to the corridor can be reached within max travel distance in one direction then applying the 45 degree rule at the door threshold would seem to indicate that two exits are available providing the final exits are within the required distance. However, you say that this is not the case. Take the door of the room away along with the wall in to which it is fitted such that the corridor becomes part of the room. We now have two exits. Build the wall back up in small incremental stages from both sides towards the middle where the original door was located. There then comes a point where we don't have an alternative exit. Where is that?
I am not being deliberately obtuse, it's just that I don't deem to be able to get my thick head around this issue.

[Mr. P]

Lyle, with ref to your scenario, I read it as; irrespective that there are at some point 2 directions of exit, the point is that the room has a single exit, therefore, the travel distance must meet that for single exit taking into count the shortest direction of exit when leaving the room. That is to say, the shortest distance if meeting the single exit criteria is ok even if the alternative direction once out of the room is furhter than single direction allows. it the toatl distance to travel but you can use the shortest for your calculation even if the alternative is further. Clear as mud still?

[lyledunn]

Thank you Mr P. Suppose you took the door away and just had an opening to the corridor.  The corridor is now part of the room. Let's say everyone in the room could make it to the opening within the max distance for travel in one direction. Escapees can then go left or right to the final exits. How many alternative exits are available from the room?

[Tom Sutton]

Thank you Mr P. Suppose you took the door away and just had an opening to the corridor.  The corridor is now part of the room. Let's say everyone in the room could make it to the opening within the max distance for travel in one direction. Escapees can then go left or right to the final exits. How many alternative exits are available from the room?

I would think it is one way travel up to the door and then two way travel afterwards the combine travel distance must not exceed the two way travel distance. It would be still limited to 60 persons because you only have one exit from the room. Table 11 says exits not doors.

[Phoenix]

Thank you Mr P. Suppose you took the door away and just had an opening to the corridor.  The corridor is now part of the room. Let's say everyone in the room could make it to the opening within the max distance for travel in one direction. Escapees can then go left or right to the final exits. How many alternative exits are available from the room?

In the above case you might also need some smoke detection as, if there are other rooms off the corridor, they will have become, in effect, inner rooms.

Also, what Tom says.  Plus, does this diagram help



Except in hotels.

[Mr. P]

Hmmm? A corridor is a corridor. Bear in mind the 3 ways to comply with regs for inner rooms. Removal of said door can be assessed as one ie providing vision panel (in a matter twists). So, would you assess a village hall with direct access from external doors as your 1st room, then any other rooms off the hall as inner? Or would you assess the hall as you would a corridor? You will in both cases still have 'X' numbers of bodies limited by your calcs to move through for exit purposes. The travel has been set by the regs but, by assessing with BS9999 you can increase numbers/travel distance by otherwise mitigating risk by use of additional safety features.
The above just as a thought provoker - not meant to confuse furhter.

[col10]

A vision panel does not necessarily alleviate the inner room situation.  The panel needs to give a sight of the outer room, to see if fire has started.  Removing the door can give more chance that someone can become aware of fire by smell and hearing and may give better sight and may justify the  claim that the two spaces are one room. 

I would consider the hall to be an access room.  A corridor is considered to be a fire sterile area because of its shape, whereas a hall suggests  a different shape which could contain a greater  fire risk .

AFD could give numbers and TD advantages and alleviate the inner room, but high ceiling heights will not alleviate the inner room situation and a VP may not and even removing the door may not.

[lyledunn]

Phoenix,
I am exporing the notion of an exit. In your diagram, forget about all the other rooms, there is just the one room where you have point A. Now remove the door and the wall in which door B is located. We are left with the two storey exits. In my case the storey exits can all be reached within the max travel in one direction. It would seem that we have also then two alternative exits from the room?? Now re build the wall in which door B was located, incrementally from both sides. At what point does the room become a room with only one exit?

[Tom Sutton]

There is no difference if you removed the door and wall, you would have to travel a certain distance one way until you had the option to travel two ways. The distance would be shorter, the minimum distance would be the width  of the room, but there is a one way component. Even in one room with two doors, when you consider the 45 degree rule, there could be the two TD's.