The need for intumescent seals on fire doors

[CivvyFSO]

I think I wasn't clear with any elements of sarcasm or what may be construed as rhetorical questions in the post. I wasn't questioning the BS, I was really questioning NT's the 2.5 minutes, essentially in line with what you say.

The way I look at it is: The 2.5 minutes as merely an 'optimum capacity' built in. i.e. The door is capable of getting x amount of people through, in y time.

[Fishy]

Thats the first evacuation strategy I have come across which has rescue or assistance factored in to the time. 

So what standard should we accept for doors? Should we create a new test for a FD2.5 door that will last 2.5 minutes of the heating regime? In fact why do we even need doors if we can guarantee that everyone is out in 2.5 minutes? I could probably prove with a bit of maths that conditions would be tenable 2.5 minutes after an alarm went off in almost any premises. Shall we engineer it perfectly so that the whole building falls down the moment the last person is expected to reach safety? After all, why do we want 30 or 60 minutes of structural fire resistance when everyone will be out?

Have a look at PD7974-6, the pre-movement time for any poorly managed premises is given as over 15 minutes. Where does this fit in with the magic 2.5 minutes? Are the people who had input to this BS wrong?

Now have a look at the details behind the recent New Look prosecution, see if people were out of the premises in 2.5 minutes after the alarm going off. 5 minutes? 10 minutes?

The fire resistance performance ratings that are in all the guidance do not equate to evacuation times & should not be used as such. The tests used to generate these ratings are not particularly ‘realistic’ (and they were never intended to be so). 

20/30/60/120 minutes fire resistance are simply rankings and which applies is based on the code-makers appreciation of the risk associated with the fire resisting element in question.  If its medium/low risk then you specify 20 or 30 min; higher risk installations attract a 60 minute rating; higher risk, protection to fire-fighters and protection of other premises is typically achieved by specifying 2 hours.  Nowhere in the tests themselves or certification of such elements does it say that they will ‘survive’ for these times in a real fire.  In fact, it’s almost certain that their performance will be completely different, because it is very unlikely that any real fire will mimic the thermal characteristics of a fire resistance test furnace (which is basically a modified gas-fired crematorium)!  ASET/RSET calculations that use the ratings as a definitive measure of fire-survivability typically fail to appreciate this point.

The good people who came up with these test methods & ratings in the early part of the last Century knew all this – the ratings are deliberately set quite high because they knew that, in the construction industry, quality of design & installation could be so variable.  Setting the ratings high, in relation to the time needed for escape when a fire is fully developed, gave some confidence that the foreseeable variation in quality control of these works would not reduce fire resistance below the necessary level.

[Tall Paul]

Intumescent seals for life safety or property safety?

I was investigating a fire in a property that was separated into different flat units.  The fire was in the ground floor flat and was impacting on the door between the flat and the stairway.  The occupier of the upper flat staed that he had to jump past the flames that were emitting from the edge of the door in order to get past it as he made his escape.  Witnesses confirmed that the fire alarm had been operating for 5 minutes before the first annoyed resident came to reset the system, saw the smoke and knocked on all the doors to clear the building.  The building was clear within 8 minutes of the alarm sounding.

The building was protected by a BS 5839-1 L2 system which had been checked for compliance 7 days before the fire.  The detector within the fire compartment was an ionisation smoke detector.  My concern was how were flames emitting from the edge of a fire door within 8 minutes of the smoke alarm operating, such that occupants had to jump past the flames in order to escape?

I was drawn towards the NIST studies carried out in the States as a result of the number of peopple who were being killed in house fires when smoke detection systems were installed and functional.

The report pointed to a set of circumstances where an ionisation smoke detector would take 20 minutes longer to detect a smouldering fire than an optical detector would in the same circumstances.  The fire ine this instance had been burning for a lot longer than 8 minutes, and the circumstances closely matched those of the NIST studies.

The intumescent strip had actuated which delayed the impact of the fire onto the stairway.  This door did not, I believe, withstand fire for 30 minutes, as discussed in earlier posts, but it certainly lasted in the region of 20 minutes.  The fact that occupants took those same 20 minutes to evacuate would support the need for strips for life safety.  Or would at least support the need for justification not to work towards fitting them over a reasonable period.

Whilst not definitive in any sense of the word, my experience in this and other investigations leads me towards encouraging the installation of intumescent seals over a reasonable timescale unless there are extremely good reasons not to.

[jayjay]

I have always belived the need for intumescent and cold smoke seals for life safety.

In the incident you mention if the seals had activated correctly and the door was a good fit then surely flames should not have passed.
I have investigated a fire in multi storey flats where the smoke has spred from a bin room through three old type fire resisting door sets and entered  flats. Non of the doors wer fitted with either seal but had the 25mm rebates which do nothing to prevent smoke spread.
There is an old BRE document Digest 320 "Fire Doors" from 1988 which is an interesting read and explains why seals are now fitted.

If you have trouble finding a copy email me.