Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 32·Diagram 2.6
Inspection hatch requirements for concealed flues
Voids containing concealed flues must have at least one inspection hatch measuring not less than 300 mm x 300 mm, with no flue joint more than 1500 mm from the nearest hatch edge.
all voids containing concealed flues should have at least one inspection hatch measuring not less than 300 mm x 300 mm
no flue joint within the void should be more than 1500 mm distant from the edge of the nearest inspection hatch, i.e. dimension X in the diagram should be 1500 mm or less
where possible inspection hatches should be located at changes of direction - where this is not possible then bends should be viewable from both directions
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