Gas boilers and appliances should be installed and fitted by a Registered Gas Installer. A Registered Gas Installer should carry out all works in compliance with the Non-Domestic Gas Installation Standard IS 820:2000. This standard requires that the installer provides a 'Declaration of Conformance' for your gas installation. This is your assurance that the gas installation has been carried out in compliance with the standard. If you have just moved into a new building or have just added a gas installation to your existing building, always insist that your builder or service provider supplies you with a copy of the 'Declaration of Conformance'. Did this answer your question? Yes No Thank you for your feedback