Conflict

[lyledunn]

I alluded to a newly refurbished ground floor city centre restaurant in another post. I was involved in the inspection activity required as part of the grant of an entertainment licence. The licence also requires that a FRA is undertaken. It was duly completed by a thoroughly knowledgeable chap and from what I saw of it, it was comprehensive and even set out some justifications. One such was the door width of a final exit required for 100. The door was 810 but the clear opening width was 780. The justification included existence  of a L2 FA, single open room where incipient fire would likely be quickly discovered, minimal travel distance and high ceilings. Along come council with their tape rule and require door is made larger. Owner points to FRA, Council officer shrugs and stays his ground. Owner shells out best part of ?1000 for remedial work and demands compensation from FR assessor!
I often hear you guys sneer about Code hugging. Maybe it is the only sensible approach in certain situations.

[colin todd]

I kind of think I am with the Council.  A reduction below 900 door leaf/850 clear opening is not about flow rate (as you cannot get fractions of people, only individual people, so it is a single unit regardless).  it is about the minimum width for flow in single file.

[lyledunn]

I am very much an advocate of prescription. In the case of door widths it is not unreasonable to err on the safe side. However, there seems so much unnecessary ambiguity in fire safety. The Small to Medium places of Assembly indicates a minimum of 750mm for 120 in low risk premises (which this was deemed to be). BS9999 indicates 800mm and seems to suggest that this could be further reduced. The fire risk assessor weighed the situation and was satisfied that the risk could be viewed as tolerable (after certain further measures were adopted). So my take on this was that the fire risk assessment would have been better conducted as a compliance check benchmarked against the highest requirement ie a door width of 850mm in TBE (NI).
In this case we had to rip out an existing door arrangement, hack off internal plaster work and decoration, fit new door and frame, door furniture, re-plaster, re-decorate and ask the client for another ?1000.
Next time the fire risk assessor nonsense will be ignored and we will stick to prescriptive criteria. So much for the sneer at Code hugging!

[colin todd]

Codes are not necessarily wrong. The fact that you do not always need to adhere exactly to them doesn't mean you can please yourself, and I would wager that all the 9999 provisos could not be satisfied.  The licensing chap was probably considering the model terms, and probably did not regard the premises as low risk for the purposes of the DHSSPSNI guide.

[kurnal]

It might be timely to remember that the original tests that were used to inform the Post War Building Studies  were based on unit widths that represented the width of a single column of people and in the old days was 21 inches for  a single column and 42 inches for a double width exit. Tests  indicated that a single unit of exit width would allow a column  of 40 persons per minute  to pass  so allowing for a normal risk building with an evacuation time of 2.5 minutes 100 persons could pass. I acknowledge that  people have got bigger since the 1930s but the problem is that the numbers and units have been converted and interpolated considerably in the various guides since then.
Yes we have a duty to ensure fire risk is reduced ALARP and if the door can be altered then perhaps it should be but to justify spending a 4 figure sum to achieve an extra 70mm width on the door is, on the face of it ridiculous.

I dont believe in compromising standards in assembly buildings and acknowledge the legislation in NI works very differently to that in England. But management and behaviour will have a far greater impact on  safety than the odd few mm on a door.

[kurnal]

So how much compensation do you think the assessor should be liable for Lyle? I would suggest the extent of his liaility would be that element of the FRA fee relating to the door in question and any loss of profit if the club was unable to open as a result of the unsatisfactory door.

[Phoenix]

I read this and was thinking, it would be good if we could get 100 people in a room with a 850mm door and see how long it takes for them to get out and then put the same people in a room with a 780mm door and see how long it takes for them to get out of there.  Then I remembered I could do this without leaving my seat.

So I opened Pathfinder on the computer and made a room hold 100 people and compared exit times for the two door widths. You can see videos of the outcomes at:

https://dl.dropboxusercontent.com/u/52634222/850mm%20door.wmv and
https://dl.dropboxusercontent.com/u/52634222/780mm%20door.wmv

The bit where they speed up in the middle is me fast-forwarding it because it's so boring watching people leave a room.

If you don't want to watch the enthralling videos, the results are - through the 850mm door the people take 107 seconds to exit and through the 780mm door they take 114 seconds.

It's important not to get too convinced by these results as the people are not inclined to panic or to push, fight and fall over as they might be in a real fire situation but the results are good as a comparison between code compliance and a little bit of stretching what might be allowed.

The indication of an increase of 7 seconds (which is an increase in RSET) could very easily be compensated for by high ceilings (which could, by some other suitable means such as fill time analysis, demonstrate that ASET is increased by more than 7 seconds above the code minimum).

The L2 system could not be used as compensation as you state that the room is open plan with good visibility so the people are likely to spot the fire before the alarm system detects it anyway.  Although, having said that, the fact that you call it L2 implies that there are some remote 'high risk' rooms so it is not impossible that the L2 system could decrease the required safe egress time.

Also, you cannot use the limited travel distances as compensation because they have very little to do with how long it takes for people to evacuate through a given exit.  Looking at my videos clearly shows that the travel distances are of no significance because everyone, apart from those very close to the door, have to join the back of a queue and wait anyway.  In fact, I have run the same simulations referred to above in rooms four times the size (i.e. travel distances twice as large) and the rooms actually evacuate slightly quicker as it takes longer for the queues to build up (the difference is only a couple of seconds and not really significant).

Maybe the fire risk assessor is liable for the cost because if he'd stuck to his guns and built a better argument then maybe they wouldn't have had to mess about with the door.  No, I don't really believe that, I don't know the full circumstances of the case.

[lyledunn]

Phoenix,
Can I pass your post to Council officer. She is one of those lovely ladies who did a degree in environmental health, received a few hours training from a certain contributor to this site then is expected to vet fire risk assessments and make determinations about the acceptability of a building with respect to fire safety. Small wonder that she prefers the comforting glow of a rigid standard.

[William 29]

I kind of think I am with the Council.  A reduction below 900 door leaf/850 clear opening is not about flow rate (as you cannot get fractions of people, only individual people, so it is a single unit regardless).  it is about the minimum width for flow in single file.

Really Colin?

I think the post below from Stu is interesting and makes some valid points. Although I don't advocate watering down standards etc to suit the client, I do feel that sometimes when we look at cases like this we can provide a suitable argument against widening a door by a few mm?

[Phoenix]

By all means, Lyle.

[colin todd]

It wasn't a few mm Wullie, it was 70mm.

[kurnal]

Yes William Colin is right - it equates to the amount he lets his belt out after enjoying his fish supper and deep fried mars bar (other chocolate coated confectionary is available)

[colin todd]

... and it will cater for the average resident of Bathmat Lock.