BS 6644:2011
Specification for the installation and maintenance of gas-fired hot water boilers of rated inputs between 70 kW (net) and 1.8 MW (net) (2nd and 3rd family gases)

https://doi.org/10.3403/30229802 (published 30/11/2011)

BS 6644:2011 is maintained by GSE/30. This standard is available from the following sources:

Other historical versions of this standard document also exist: