Fire escape stairs in buildings

If your building is modern I would expect it to be fitted with a stairwell pressurisation system. probably a fan at roof level. It will only kick in if the building is on fire.

Keeping the stairwell access doors closed will aid maintaining a positive pressure.

One assumes that in a 22 storey building, there is more than one escape staircase.

Fire protection and safety are a key part of building design and designers work on creating "safe zones" for users to escape to.

They work on both horizontal and vertical escape strategies, and have strict horizontal travel distances before getting to safe zones.

I would also expect that the fire escape doors are linked to the fire alarm, so when triggered, the doors are released from their stoner status, to enable escape to other safe zones

I wondered about that. My imagined scenario now includes a total power failure (the explosion that starts the fire, also knocks out the power) so no pressurization can happen.

The pressurisation concept also seems at odds with Jason's idea of a smoke vent at the top of the stairwell. I wonder which it is. Chimney damper open when there is a fire to ensure a good healthy blaze?; or does the blower kick in to force feed the flames? 

Yep, a number of stairwells. But my nightmare is being trapped in one of them. The others are no use if I can't get to them. Not sure if our stairwell doors unlock with a fire alarm. I might look into that.

Originally Posted by winkyincanada:

       
Hi Winky,

The stairwell is a 1 hour fire shell in standard public buildings. The doors leading onto the stairwell should be  at least 1 hour rated with a smoke seal around the door, self closing and therefore should never be propped open. Today a new stair well built should also have an automatic smoke window at the top or vent to allow smoke to be let out if any entered the stairwell. Depending on the occupancy level and distance to the protected stairwell, two may be required.

All in all they are an excellent fire escape device, but one can't remove the risk entirely. Britain actually has very strict fire regulations for new buildings and is always a hurdle to try to accommodate them without often affecting the architects ego trip

Cheers

Cheers

I'm not so much worried about being burnt, it is the asphyxiation that I see as the major risk associated with being trapped in a chimney with a fire burning at the bottom.

Ah yes..."should never be propped open". But when walking down I see people holding doors open all the time. Would they continue to do so until they were overcome by smoke and collapsed into the doorway, preventing it from closing? I don't know.

I hear you about the architects. Out stairwells are very compact with 4 flights per floor. I thought I was going to collapse of dizziness before reaching the ground floor. 'round and 'round and 'round we go.

I thought you would mention that. The fans will be powered from an essential supply, which is more robust than the power to the general ventilation fans. But, I suppose if the building has exploded with loss of all power I guess you're screwed anyway.

No system is infallible, but there have been enough fires and deaths in large building for the people in the know to come up with the correct fire strategy.

Checking the doors during a fire alarm may not give you the answer. The doors might not unlock on first knock, but only unlock on second knock. I think a false alarm is likely to be first knock.

Thanks. Yeah, the recent one was kind-of a false alarm, but a smoke detector did correctly detect smoke when a piece of equipment failed (burnt out) in the basement. No ongoing fire that had to be extinguished, though (from what we were told).

On another point it was a LONG time between the preliminary notification and the actual instruction to evacuate. I can't really understand why the verification took as long as it did.

I thought fire doors (in the UK) had to be able to be opened mechanically, usually with a push bar, and should not be locked either mechanically or electronically.

It is also usual that people try to leave a building the way they come in, this can result in some stairways being very busy where others are hardly used.

First knock is when one detector goes off, second knock is when two detectors go off. Maybe your building fire strategy only requires evacuation on second knock.

Perhaps you could be cheeky and ask to see the buildings fire strategy.

I had "assumed" that any doors giving access to a fire stairwell either had to give free access at all times to/from the stairwell, or if they were electronically.magnetically locked to prevent access from the stairwell during normal occupancy, they had to automatically release on sounding the fire alarm (eg the electrical magnet is released on power -down or loss-of-power). This should allow people to transfer fro one fire escape route to another via any intermediate floor.

Self-closing doors seem to be a requirement, but if non-thinking people prop a door open thus allowing toxic smoke to fill stairwell(s), then I guess its down to the action of a trained fire-warden to get the door closed.

Not perfect, and it often takes the "naive" question from a non-expert (aka Winky) to generate a change-making discussion.

Cheers

Don

Just checked the lock on the stairwell door near my office. A big beefy mechanical lock. No solenoid override or electromechanical latch evident at all. Without a physical key there is no way to get out of the stairwell onto the 22nd floor, short of breaking down the door (which would be very hard as the door is extremely solid). You'd be trapped like rodentia. Other levels may be different.

That is almost certainly illegal.

All that I have said above also refers to smoke ingress and not just fire.

Additionally, if you have an open plan office that leads straight into a fire escape stair well  there should be a fire lobby between the open plan office and the door leading directly into the stairwell, also to try to prevent smoke ingress into the stairwell.

Cheers.

Hmmm, Winky hasn't posted for 22 hours.

Hope he hasn't locked himself in the stairwell. Or worse still, been locked in a stairwell by an irate facilities manager disgruntled by somebody sticking their nose into his business.