Technical Booklet L Combustion Appliances and Fuel Storage Systems·Page 62·4.22
Provision of flues for gas appliances
Gas appliance flues and flue pipes must be designed and constructed either following the specified provisions in paragraphs 4.23 to 4.28, or if using factory-made components for a new known appliance type, those components must be independently certified to meet performance standards in Table 4.4 and installed per manufacturer instructions.
The flue and flue pipe for a gas appliance should –
(a) be designed and constructed following the provisions on the selection of components and the manner of their installation as given in paragraphs 4.23 to 4.28; or
(b) if the intended appliance is new and of a known type –
(i) be built using factory-made components that have been independently certified as achieving a performance at least equal to that corresponding to the designation given in Table 4.4; and
(ii) be installed in accordance with the provisions of paragraphs 4.25 to 4.28 and Section 2, as relevant, and in accordance with the appliance manufacturer's and component manufacturer's installation instructions.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet L - Combustion Appliances and Fuel Storage Systems.pdf