The standard provides definitions of terms used in Institution of Gas Engineers and Managers (IGEM) standards and guidance documents.
The standard recognises inconsistency between definitions within IGEM Standards issued up to September 2009 due to the time period over which those Standards were developed. It attempts to consolidate the varied use of different terms across IGEM Standards, to provide a base for their future amendment and to represent current best practice.
Definitions contained within such an IGEM Standard published prior to 1st September 2009 may continue to be used until such time as that Standard is made obsolete. Where an IGEM Standard is published on or after 1st September 2009 and does not contain definitions, then the IGEM/G/4 Standard applies.