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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Fire Safety => Topic started by: Archie2017 on January 18, 2017, 09:51:40 AM
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Apologies if my question is very basic.
I am undertaking some fire safety design as part of my studies and have a couple of questions in relation to ADB diagram 7.
Looking at the diagram, it appears its objectives are to limit the TD to 7.5m from the Apt entrance to the stair enclosure and have the area immediately adjacent to the stair ventilated.
What is the difference between a protected lobby and a protected corridor?
Can I have a single stair with a ventilated lobby (albeit as the shape of a corridor) on either side of the stair keeping the TD at 7.5m?
I still would have 2 sets of fire doors as separation being the door to the Apt and the door from the lobby / corridor into the stair.
This would allow me to use windows as AOV's in my design and remove the requirement for a smoke shaft from the central point as shown in ADB 7a but would still meet the design objectives of Diagram 7.
Once again apologies if I am asking a stupid question.
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Do we meet again? Check out http://www.coltinfo.co.uk/sca-guidance-2-video.html?submissionGuid=695021a0-fbee-4ec7-afa3-141f80471af8 the webinar may be useful.
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Sounds ok to me Archie, the key features are the travel distance and the ventilation . It doesn't matter what shape the space is, a corridor is fine. The 7.5m applies to the travel distance for people, the space, and distance to the vent can be bigger than this. As Tom points out much work has been done one this by the SVA and there is guidance available on their website. Colt and others bring alternative solutions to the table, including smoke extraction systems often working on an intelligent pull or push system depending on the location of the fire. I have seen the lobby extended as far as 45m in each direction using such a system, it was approved despite my objections to the parameters used.
When I was trained in the 1970s they used to call these distances "the 7.5m dash" and it was explained that this distance was survivable in the unlikely event of the fire service needing to assist residents to escape. Hence the dash was shorter where the lobby was unventilated. It always sounded like a load of boloney to me.
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Since then, the rules for ventilation were re-visited and it was recognised that the ventilation mainly provides protection to the stairway.
The distance is kept short for a similar reason. if you need to leave when the space is smoke logged then you don't want to go too far. the numbers haven't changed because there's no better data.
as for protected lobbies and corridors, they are interchangeable.