This standard covers hazardous area classification for gas metering equipment and applies to meter installations containing Natural Gas in the gaseous state at maximum operating pressure not exceeding 75 bar. It covers primary and secondary meter installations, associated volume conversion equipment and all associated electrical equipment and connections, in industrial and commercial premises which have been installed to other BS and IGEM standards as appropriate. However, it does not apply in the following circumstances, where IGEM/SR/25 should then be used instead:
- Ventilation is of the forced type
- MOP exceeds 75 bar
- Creep relief vents terminate within a meter installation’s housing
- A competent person considers there to be unusual site circumstances
- The installation is at a remote and unmanned site
- It is considered that leaks may go undetected
- Un-odourised gas is metered.
This standard may be applied for meter installations in existing premises where ventilation is present but where it is difficult or impossible to confirm that the levels of ventilation comply with current design standards. It uses a methodology that assumes meter installations are protected from external interference and located in populated areas, or sites are manned in industrial and commercial premises, leading to a high likelihood that any gas leak will be detected within a short period of time. It contains information about legal considerations and then extensive details of the concept, requirements and classification of hazardous areas.