Glazed fire door - Can we avoid upgrading by evacuating quicker?

[Tom Sutton]

One for you risk assessors this is how Joe public thinks, what do you think;

I am attempting to seek some advice regarding one of our entrances to our business.

A few years ago, our business had a glazed front door installed with the mind set that it was Fire Resistant (FD30). We have been recently made aware that the glazed door is not fire resistant and have been requested to take suitable measures to bring the entrance into line with regulations. The position of our business means that the entrance in question comes out onto a fire evacuation staircase so there needs to be some form of fire prevention to ensure that people on the floors above can still use the staircase safely in the event of a fire.

Short of us replacing the door, would the installation of additional pre-warning systems be sufficient in adhering to regulations?
The thinking behind this is if additional systems were installed triggering alarms sooner in the event of a potential fire, the building will be cleared quicker meaning no potential risk to those attempting to escape past the entrance.

Would this line of thinking would be sufficient enough or will the door have to be redone with the correct Fire Resistance?

[nearlythere]

Short of us replacing the door, would the installation of additional pre-warning systems be sufficient in adhering to regulations

Your client would be bringing little to the table to compensate for the lack of protection of the stairway but he has a point, to a degree. Why 1/2hr doors when the evacuation time would be much less and in many instances much much less. It's that non prescriptive guidance document again and the IOs and judges who can't seem to see past it.

[Davo]

Hi Tom

Surely the door will be cheaper?


davo

[Tom Sutton]

NT I don't have clients its something I spotted on another forum. I personally would have needed much more information and most probably would have said " no way Jose " and  asked for smoke seals. How long would it need to evacuate the building and which early warning device would give that sort of pre-warning.

Davo good point.

[CivvyFSO]

The half hour requirement for FR is little to do with evacuation time. First of all, as we are all aware but need reminding sometimes, FD30S is simply a grading attributed to a door for performing a certain way in a specific test. A normal growing fire would probably end up taking more than 30 minutes to break through the door. But if conditions are right for flashover to occur then, depending on fire loading, the radiated heat from such a fire could be far in excess of what the door is subjected to in the test, and it may fail quite a while before.

It is additional protection for when things go wrong, and things will regularly go wrong all over the country. i.e. people ignoring fire alarms, fire alarms not working, an injured person somewhere etc. This probably happens quite often, and people will be (silently and unknowingly) saved by the presence of a nice big chunk of wood between them and the fire/smoke.

If someone wanted to take the approach of ensuring that people are out before they are affected by smoke, then they need to qualify that with a proper ASET/RSET comparison. If the glazing offers no fire resistance, then they are going to struggle.

So my actual opinion would be, if it is standard glazing, the door needs replacing. If it is FR glazing but no strips & seals, my decision would then be based on the numbers of people relying on the escape route, the number of floors, the type of occupancy relying on the route, and the likelihood of co-operation between the parties. Or.. If you show me a ASET/RSET comparison that shows that this is safe with normal glazing, I will send it back with large swear words on it in crayon.

So, it's a great big "it depends" from me.

[Phoenix]

What Civvy says.  We don't want people just getting out in time.  We want them to have loads of time to get out. 

In traditional engineering fields, safety is often achieved through over-engineering.  In other words providing what is referred to as 'redundant' safety factors to allow for failure of some element(s) of the system without compromising safety.  I don't like the term 'redundant' myself because I don't think these features are redundant, I think they are simply additional protective measures.  But anyway, this is what fire safety is about, providing resilient and robust (to borrow words from management-speak) systems. 

Also, it may be that this staircase has (or should have) disabled refuges in it. 

But on the other hand there might be another eight staircases in this building and losing this one might be of no significance whatsoever (after all we accept a reception desk actually within a staircase if everyone in the building can get to another staircase). 

Stu

[Tom Sutton]

I agree with Civvy "it all depends" but what I am reading is all theoretical. What about the practical aspects if you calculate the evacuation time of 15 minutes how would you achieve this. Allow standard doors and AFD which may last the required time or protect the staircase with fire doors and accept the over engineering. As for ASET/RESET concept has its critics http://onlinelibrary.wiley.com/doi/10.1002/fam.1025/abstract I suspect because the lack of reliable data.

Being a very old dinosaur who has witnessed many fire evacuation drills (a service we used to provide) I would estimate between 10 to 20 mins in a small/medium building therefore I would require FD30 doors being the lowest standard available for all staircases, over engineering I accept.

[CivvyFSO]

I don't think that it is over-engineering Tom. It is a reasonable factor of safety to account for unexpected occurrences.

Changing the subject slightly...

I agree to some extent with the ASET/RSET criticism. Fire engineers often treat the output of equations far too literally. These things should be subject to sensitivity testing. i.e. What happens if we have a fast growing fire instead of a medium fire? What happens if people don't move as quick as we think? What happens if the sprinkler system doesn't control the fire? What happens if the fire is in the corner of the room?

Playing devil's advicate a bit: (Only based on the abstract from Toms link) It would be fair to say that where fire deaths have occurred, people have indeed not walked out in the robotic fashion that the codes behind ASET/RSET suggest they would do. But is this taking into account the statistics involving the number of fires where people have not died or been injured? How many fires do we have where nobody is hurt? Aren't 80% of fires not even reported to the fire service? Do we have to cater for the person who goes and locks themselves in a cupboard if they smell some smoke? Do we have to cater for the person who chucks a pan full of water on a fat fire? Fire safety is about what is reasonably practicable, and looking at almost any fire death in hindsight will show a death that was preventable had we known that those conditions would occur.

[Midland Retty]

That's very true. The concept of "resonably practicable" can sometimes be lost.

I've never been a fan of the "ASET/RSET" , perhaps not so much the concept itself but the way in which some fire safety professionals interpret the data.

Tom I wouldn't say you are an old dinosaur, your logic seems quite sensible to me. I suspect most have us have witnessed evacuations on this forum, and will testify that they are very rarely achieved in the fabled 2, 2.5, or 3 minute time frame HMG guides tell us we should achieve!

[CivvyFSO]

If you think about it, in any premises that is filled to capacity, the exits are sized to allow this 2.5 minutes as an absolute best case scenario. i.e. The moment the 'evacuation clock' starts, all persons are immediately at the door queueing to leave, and maintain the optimum flow through the exits.

This really shows that if a premises is at its capacity, then by design, the 2.5min evacuation is quite unlikely.

[SamFIRT]

The moment the 'evacuation clock' starts, all persons are immediately at the door queueing to leave, and maintain the optimum flow through the exits

& all the exits at that! 

It's impossible to calculate evacuation times with any meaningful degree of accuracy due to the human variables. So pre warning systems are worse than usless as they will be ignored.

The evacuation times take no account of human behaviour. Nor the fact that people ignore alarms and seek reinforcement of the message in the pre movement time. Neither do they take account of variations in speed of the evacuees and above all it is assumed that people will use the nearest exit.

They don’t. Not in the real world they don’t. They all seem to in computer models though.

Not that I am arguing against a good door. ..oh no……A good door will save more lives than a good firefighter anytime.

Buy time with a good door.