Discounting Exit due to Fire

[deenee]

Hi All,
I am looking at a layout where two exits are located within 10m of each other. Can one say a fire at mid point of the two exits can discourage people from using both and so the two will have to be discounted? The buildig is sprinklered therefore the fire spread is likely to be limited but this may not be important at the early part of the fire when escape is crucial - although BS 9999 would indicate it is important.
The room has other exits so the 45deg rule is not a factor.
Your take on this is appreciated
Thanks

[kurnal]

I think it entirely depends on the size geometry of the room and the use to which it is put, together with the nature and location of the fire risks that could be percieved. Sometimes the two doors may need to be considered as a single exit and sometimes not. Happy to comment if you pm a sketch.

Sorry this isnt very helpful but its the best I can do with the information as given. 

[CivvyFSO]

The room has other exits so the 45deg rule is not a factor.

The 45 degree rule is still a factor when working out if both exits should be discounted. If the exits are within 45deg of each other as shown in ADB, then they are essentially seen as one exit, and if their combined capacity is the largest capacity, then it is those exits that should be discounted. However, as mentioned, certain room geometries might make it so that one fire cannot reasonably be seen to take both exits out, so some common sense should come in to play. You seem to be answering your own question.. Since there is some doubt in your mind as to whether a fire can take out both, I would err on the side of safety and assume that it can. (But I am not in the business of saving clients or employers money or increasing occupancies

A sprinkler system does little to avoid this, as it is quite some time before the system will activate, you might be looking at flames of 1-3m, enough to discourage people from walking in that direction, and hopefully people would be well on their way in the opposite direction by that point.

[deenee]

I think it entirely depends on the size geometry of the room and the use to which it is put, together with the nature and location of the fire risks that could be percieved. Sometimes the two doors may need to be considered as a single exit and sometimes not. Happy to comment if you pm a sketch.

Sorry this isnt very helpful but its the best I can do with the information as given. 

Kurnal thanks for your input and offer to hlep. I will PM you with the sketch - though I am a novice in this forum so will have to learn how to attach file when sending PM.

[deenee]

But I am not in the business of saving clients or employers money or increasing occupancies

Without that we wont put food on the table - now that clients are more bullish wanting safe and imaginative buildings that are cheaper overall.
How that is achieved? They will say, well that is your problem - you are a fire engineer and that is why we employed you.

[Mushy]

deenee...I'm sure you will get an answer from civvy soon enough

don't think civvy is in the 'client' business

[CivvyFSO]

I have 'started' typing many replies, but then usually thought better of it.

They were generally along the lines of "The client might also say 'We are paying you for your expertise, why are you on an internet forum asking strangers their opinion on what is essentially a very simple issue?' And also as issue that you got one of the main principles blatantly wrong to start with.", but I thought that it might be seen as argumentative or insulting and not particularly welcoming. So I decided not to.

[CivvyFSO]

DOH!   

[BLEVE]

You argumentative, insulting & unwelcoming . Am shocked how unlike you 

[CivvyFSO]

You argumentative, insulting & unwelcoming . Am shocked how unlike you  

In the same spirit of Clevelandfire3's night time postings:-

pu yuors

 

[BLEVE]

póg mo thóin
 

[CivvyFSO]

Shan`t.

In a vague attempt to keep this thread on-topic:

I wish YOU were discounted due to fire!

(The moderators can complain all they want, THIS is what the internet was made for!)

[BLEVE]

Civvy you are a legend in your own mind,the only time I will be discounted by fire will be at a crematorium.

By the way wrt the topic of the thread, I think that Civvy summed it up in his first reply.

 

[Phoenix]

Just staying with the topic - I think kurnal and Civvy have summed it up pretty well but I would just add that this 45 degree rule is very much a rule of thumb - there is nothing magical about the angle of 45 degrees.  The 45 degree rule is a statement of the relationship between the distance between exits and the maximum travel distance within the room.  It cannot be hard and fast and must not be rigidly adhered to because it is much to simplistic to truely reflect reality. 

In reality differing ceiling heights can affect the potential for a single fire to obstruct two or more exits, so too can the arrangement of furniture and other contents of the room (it is not often that people can move directly towards an exit) and so too can the nature of the contents of the room (potential for fast fire growth or slower fire growth?).  Civvy gives good reasoning for why sprinklers are unlikely to be an important factor (irrespective of 9999's take on it).

Personally, I use the 45 degree rule as a starting point but I keep in mind the other factors that contribute to determining if two exits might be lost to a single fire.

The original post has the two exits at something like 10m apart.  That's quite a distance and even in a largish room it would unusual for both to be discounted together, as a single exit.

Stu

[nearlythere]

All this talk about a room having two exits. Many rooms have two or more exits. Not all necessary for escape purposes but for convenience.
Why has it more than one exits? Is it because of occupancy, travel distance, level of risk or because of nothing more sinister than it just happens to have more than one way in and therefore more than one way out.
Taking into account occupancy, travel distance, and risk level, is it possible that just one of the exits, any one, would be sufficient?