If you have just moved into a new home or have added a gas installation to your existing home, insist that your builder / developer / installer provides you with a copy of the 'Declaration of Conformance' for your gas installation.
This certificate is a requirement of Domestic Gas Installation Standard IS 813, a copy can be purchased on the NSAI website. This confirms that your installation complies with this standard. You should keep this document in a safe place.
It is a legal requirement that any work on gas installations must be carried out by a Registered Gas Installer.