Gas Vents in Service Ducts

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    Nicola Caldow

    In one of our sheltered schemes we have a service duct (1 foot square) next to each flat that contains just a gas pipe. As there are 30 flats in the building spaced over 4 storeys there are 7 of these risers in the building going from the ground floor to the roof. Previously on each floor there had been a plywood door on the duct with a vent at the top of the boarding. This lead directly onto the corridor which is the main means of fire escape. Following a fire risk assessment it was stated by the assessor that the shaft holding the gas pipes can’t ventilate into the means of escape (BS9999 ‘ 32.5.15 9c) – ‘a protected shaft conveying piped flammable gas should be ventilated direct to the outside air by ventilation openings at high and low level’. The problem is that the shafts do no feed directly onto the outside of the building. At roof level a vent to the outside air could be organised but at a low level it is nearly impossible because the shafts are in the middle of the building. Does anyone know of any ways around this problem? Regards

    Kim Morris

    Lots of things to consider here before an assessment of the current situation can be made, for instance is this installation pipework or service pipework? You would also need to consider the size of pipework and the cross sectional area of the duct, type of material that has been used, is it continuously welded or screwed? Various regional differences might also apply in some circumstances. My first point of contact would be to get some advice from your local Building Standards office with regards to ventilation and protective shafts.

    Peter Sandry

    Is this a ‘protected shaft’ or is it fire sealed at each compartment? You state that at each floor there is a door, not taking fire regulations into account, if a door is fitted the space behind is no longer a duct and as such does not need venting. I have had this confirmed during a Gas Safe site visit,

    As Kim has stated you may also need to look at pipe construction and joining method for suitability in escape routes. Consideration into the use of Trac-Pipe or similar, providing no joints, may alleviate the ventilation requirements.

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