Without testing, one can not reliably
say how effective the sprinkler at the
top of the elevator shaft would have been.
Especially if this car recalled to the bottom
of the shaft; sprinkler water would primarily
wet the walls if this was a one car shaft.
Then there is consideration of shielding that
the roof of the elevator car provided. Probably
too many variables to say what the advantage
or stalemate would have been.
Had the car returned to the primary recall
floor and opened its doors, this would have
provided valuable oxygen that otherwise was
more limited had the fire burned in a closed shaft.
Then again, a closed shaft would have reduced
entrainment, and kept the smoke hotter.
Certainly sprinklers in the corridor near the
elevator car doors would have helped reduce
the HRR in this case, although there is the liability
of putting lots of water into an elevator shaft with other
cars. The scrubbing benefits
from sprinkler water might be measurable on
soot and smoke temperature, but virtually
ineffective on CO dispersement. You have no
support here, for the water curtain strategy.
As mentioned by CC, these fires are extremely
rare, such that in the case of at least high-rise
buildings where:
a. elevator shafts should be surrounded by
smoke-resistant lobbies, and
b. cars should be noncombustible,
if a fire does occur, the smoke should not spread
in untenable amounts past the elevator lobby, with
the result that the remainder of the building stays
tenable (at least for the duration of egress) despite
one evidently plausible worse case elevator-system
fire presented to us.
Before deciding to return to a sprinklered elevator
shaft, we should weigh in the advise from professional
research projects focussed specifically on elevator
system fire safety, as this is an active field of
investigation at the moment. One fire does not warrant
a change in risk categorization for elevator system
fires.
Lesson learned: remove combustibles from elevator cars,
shafts, etc. NOTE: this is not an endorsement of Fire Retardant
chemicals (for reasons related to the environmental
costs of generating and applying these chemicals)
in lieu of removing combustibles. An it is realized some power
cables are run inside elevator shafts, and they will remain.
New building designs should consider tenable egress from
elevator fires (what if someone is moving a couple of sofas
in the elevator). One approach is emergency notification
and exit placement such that this situation is not repeated
[where students (a rather robust occupant) were afraid to
use the corridor and exit to a stair (apparently on a floor remote from
the fire) because the corridor was too choked with black
smoke (a surprising finding to my intuition)] under non-stack,
non-wind conditions. Alternatively, a smoke control design could
be as simple as constructing a passive elevator lobby with
active doors held open by magnetic hold opens. Both the exit
and smoke control approaches require sufficient documentation
to validate their probability of success in the light of building
maturation (i.e.under duress of some component failures) as well
as performing simply in the line-of-fire.
There are enough details and interrelated
disciplines (elevator, mechanical ventilation, electrical
backup power supplies, egress, and good old-fashioned
sprinkler protection) that making an out-of-hand
prescriptive design paradigm from this case
might be short sighted, though that should not stop
us from suggesting potential strategies for peer
review.
scot deal
excelsior fire engineering
_______________________________________________
Sprinklerforum mailing list
[email protected]
http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum
To Unsubscribe, send an email to:[EMAIL PROTECTED]
(Put the word unsubscribe in the subject field)
