Reference to Directive DTU 24.1 P2, February 2006 and CSTBat advice (July 2008 editon)
5.4 Implementation of metal connecting flexible pipes
The connecting flexible pipe must be compliant with the XP D 35-311 norm.
The connecting flexible pipe can be used to connect appliances burning gaseous fuels, functioning in passive stack ventilation, except in case of a possibility of temporary condensation in the connection pipe (i.e. a condensing boiler, a low temperature boiler). In this case, it is recommended by the CSTB regulation to use the INOX 304 and 316 product family
The connecting flexible pipe has a special tag for gas, affixed by the manufacturer, to identify it. It is sold with installation and use instructions notice.