Any gas boiler, steam boiler or furnace that uses natural gas should be fitted with a gas train that meets British Standards BS 5885. Testing requirements for these boilers depend on the components and type of your gas train.
If you are the owner of such a boiler (including a dual fuel-gas firing boiler), you need prior approval from MOM before you can install or modify.
As part of your application for approval, you will need to submit a detailed piping and instrumentation diagram of the gas train, including a full legend.