when is a corridor just a corridor?

[kurnal]

I can agree with both sides of this argument to some extent.
My view on it is this. As far as the designer of the building is concerned Jokar has it spot on. But then someone occupies the building and chooses to use a nice wide  corridor for storage, furnishings, mail room, rest area, waiting room or whatever. In these circumstances the decision is then:
1- If its a protected corridor its not acceptable. remove fire loading.
2- If its not a protected corridor could the building still comply with guidance (travel distance, vision panels, smoke detection,  obstructions and escape route width, and rules for staircase protection) if the corridor were to be treated as an access room and all rooms off the corridor treated as inner rooms?

If it can meet the guidance in other respects I too, like Steve, in that particular case would probably treat the corridor as an access room.

[ps]

Ah - this is now full circle! Kurnal - you've hit the nail on the head!  But, back to my original question - when is a protected corridor a protected corridor??  What makes a corridor protected and in what circumstances does a corridor need to be protected?

If you can answer these couple of questions, I'm sure Santa will be good to you this year!

[PhilB]

Basic principles used to be a protected corridor i.e. one that provides 30 minutes fire resistance between the corridor and all rooms except low risk wcs required in dead end conditions and sleeping corridor.

Most now agree that for dead ends not the best solution, especially if no AFD.

Sleeping corridors should also be protected routes to buy time for escape.

Also single stairs, tall buildings or those using phased evacvuation usually would require protected lobby or protected corridor approach to stairs.

But I agree with the earlier points that a corridor is a corridor. A corridor that has no fr provides additional protection to a stair case even if the doors are open. The premise being that fires occur in rooms, not corridors, thats why they should not contain significant fire loading.

Smoke pressure is reduced as it moves from room into corridor so corridor performs same function as a lobby.

[steve walker]

I found this in ADB:

"Enclosure of corridors that are not protected corridors

4.22 Where a corridor that is used as a means of escape, but is not a protected corridor, is

enclosed by partitions, those partitions provide some defence against the spread of smoke in the

early stages of a fire, even though they may have no fire resistance rating. To maintain this defence

the partitions should be carried up to the soffit of the structural floor above, or to a suspended

ceiling, and openings into rooms from the corridor should be fitted with doors, which need not be fire

doors."

" ... in the early stages of a fire ..." It needs to be considered how long the smoke and heat will stay in the room and when escape through the corridor is feasable.

I think that the likelyhood of the door being left open is significant and should be considered in the risk assessment.

Phil,

I can accept that, especially in the early stages of a fire, the smoke pressure should be lower in the corridor than in the room containing the fire load. However I would hope that a proper fire resistant lobby provided significantly better protection.

[PhilB]

Phil,

I can accept that, especially in the early stages of a fire, the smoke pressure should be lower in the corridor than in the room containing the fire load. However I would hope that a proper fire resistant lobby provided significantly better protection.

Quite so Steve, of course a FR lobby would give better protection and that is why it is required in the examples I quoted.

[AnthonyB]

Ah - this is now full circle! Kurnal - you've hit the nail on the head!  But, back to my original question - when is a protected corridor a protected corridor??

In the old days it was simple - because the fire certificate plan said so!

Good comments by all the above, very useful

[ps]

many many thanks to all who contributed, I will now go and lie down in a darkened room!
I think reading on, in and between the many lines is that corridors are never rooms if they lead somewhere. Protected corridors are only needed where there is significant risk of fire, sleeping accommodation, and for the enclosures onto stairwells. Other corridors that could be used as escape routes need to be kept clear and fairly free of fire loading in case they need to be used in an emergency.

If someone could just say yes, I'd be sooooo happy!


Thanks in advance.....

[kurnal]

If you were to ask me on a monday I'd say yeeeeeees..........

Add to your list of protected corridors:

corridors where there is only one direction of escape possible

corridors forming part of an escape route where parts of the accommodation are further than the maximum recommended travel distance from the nearest exit- ie excessive travel distances

[ps]

Thanks Kurnal - I've been distracted by other things since, so haven't been back to the site - but just found your reply...many thanks again perfect!

[nearlythere]

A corridor is just a corridor when it provides a means of intercommunication between habitable rooms or those where a function is undertaken. An area which is the same shape as a corridor but is used as a place of work or habitation is a long narrow room. A long narrow work room where people work or where a function is undertaken can be an access room to a square shaped office off it.
Lets say someone who has three offices off a corridor needs more room and decided to move a receptionist with all of their equipment into the corridor. The corrider then becomes an office, albeit long and narrow, and the three offices then become inner rooms to the now long narrow access office. Providing the travel distance is met and there is a VP between the inner and access room or AFD in the outer room whats the problem?

[Martin Burford]

nearlythere.....Is this a dead-end corridor in your imagination ?
Conqueror

[nearlythere]

Conqueror
No. It is a long narrow access room which has an inner room and the travel distance is up to 18M from the innermost point in the latter to the exit from the former. A room does not have to be a particular shape or size. Are all single exit rooms dead end conditions? Yes but an acceptable dead end if the travel distance is met.

[kurnal]

I'm just about with you in principle nearlythere- but there are some significant caveats. You are right that there is no defined shape for an access room but the rules for dead end corridors have always been stricter and for good reason. And that gives us a pointer as to why there may be a small problem with your suggestion.

First thing is  that it all depends on the risk you are putting in your long narrow access room. You will have to pass close by the risk to reach the exit. In a more regular access room you could give the fire a wider berth.

In a more conventional access room situation the room would have a much greater volume  into which the smoke and heat could spread in the early stages of a fire, thus maintaining tenable conditions for far longer than would be the case in a long narrow corridor shaped access room. I would take this into account and think very carefully about the time it would take to detect, respond and move away from the fire to reach a place of safety, and how quickly untenable conditions would develop that could prevent egress.

I think the outcome for me  would be to minimise the risk, or  move the risk out of the access room as far as possible and to look at the time to exit vs tenability- perhaps a reduction in travel distance may be justified as the access room narrows?

finally  vision panels are rubbish most of the time and ADB allows them to be miniscule - but remember that a  vp may not give much of a view of your long narrow access room especially if its configured like a corridor- you may not see more than across the width of the corridor. Smoke detection is a much better bet.

[nearlythere]

Funny how such a simple issue can lead to so much discussion. But it is good to exercise the mind on simple things for a change.
You are quite correct in rubbishing VPs because of the many, many conditions which would have to be met for them to be practical, eg. position of inner room occupants, any visual impairment, location of furniture, size and position of VP etc.
The matter again of the long narrow access room and your suggestion on the removal of any risk from it. COPs will say that the access room should not be an area of special or high fire risk. I wouild not neccessarily consider normal office equipment as being of a special or high risk catagory.
For code compliance I would suggest that my arguement holds water but for RAs your view is quite valid.

It's good to talk.

[ps]

There's me thinking I asked a simple question!

Can I ask another - I'd like to get into this fire safety a lot more as I'm increasingly getting drawn into debates. Other than swallowing the guides - what else should I be looking to do to become "competent"? In addition to regularly logging onto, and getting expert views from you lot of course! Is there a generally accepted good all round qualification respected by all?