Corridor Ventilation

[GB]

Is the purpose of ventilators within the corridor adjoining a protected stair to provide make up air for the stair and stair vent or in fact to ventilate the corridor? I thought the former but I may be wrong

If so should the window be bottom or top hung?

[Tom Sutton]

Check out http://fire.org.uk/forum/index.php?topic=1748.0 its about the BRE research report summary Smoke Ventilation of Common Access Areas of Flats and Maisonettes which I think would be relevant in all buildings. The report summary at http://www.bre.co.uk/filelibrary/pdf/rpts/partb/Smoke_Ventilation.pdf

[CivvyFSO]

They are to ventilate the corridor.

Read the BRE report summary.

[kurnal]

My simplistic summary would be thus.

Fires cause thermal expansion and convection  which create an increase in pressure at high levels within the room involved.
Fires usually occur in rooms and not in lobbies or staircases because we keep those areas clear of combustibles.
If a fire occurs in room the increase in pressure will push smoke and products of combustion out through the door and other openings into the space beyond  in an attempt to equalise the pressure.
If we put a vent in the lobby such increase in pressure will be released harmlessly from the vent  to the atmosphere and therefore smoke will not be pushed into the staircase.

In summary the vent is provided in the lobby to release the pressure and thus protect the staircase.

As people will open doors into the staircase as they escape it is possible smoke may enter the staircase as they leave, so the vent in the staircase will allow that to escape.

After all we would not want to source make up air for the staircase from the very location of the fire.
I know it is a gross over simplification but that is my understanding of the BRE report.

[CivvyFSO]

I think that Kurnals explanation is particularly good, and it demonstrates why this vent is most certainly NOT make-up air for the stair vent.

Another way to look at it, ask colt whether they set their mechanical fans on 'suck' or 'blow'

[Tom Sutton]

You mention, should the window be bottom or top hung, this being so I would think it is more likely to be there for the use by the FRS to improve working conditions when fighting the fire or clearing the smoke after a fire.

[kurnal]

Bottom hung is recommended.