Natural gas is one of the mainstays of global energy. Where it replaces more polluting fuels, it improves air quality and limits emissions of carbon dioxide. In this analysis, we explore how widespread and durable this role might be in some of today’s key energy markets.

All the piped medical gas supplies to theatres and other areas finish in special terminal units with a non-interchangeable coupling; in the UK this is a type of Schraeder valve.The non-interchangeability is achieved by the use of various sizes of collar on the probe so that a given collar only fits the appropriate outlet; thus the nitrous oxide collar has a larger diameter than the oxygen collar, as shown.

Outlets are also labelled and colour coded and contain an internal valve which seals the gas supply until the probe is plugged in. On unplugging, the valve closes off the gas supply.

The gas supply system is more vulnerable to deliberate attack than coal or petroleum supplies, but it is more robust than the electric system. It is less vulnerable than the electricity system because it is mostly buried underground, it can be used to store gas (line pack), and it can use relatively secure depleted oil and gas wells for storage.

Like the electricity industry, companies in the gas business have long recognized and effectively planned for contingencies that mitigate terrorism. Spare parts are generally kept on hand to effect quick repairs. However, the potential vulnerabilities in gas system supply are illustrated by the August 2000 rupture and explosion caused by corrosion in a 30-inch gas pipe near Carlsbad, New Mexico, killing 12 people.

This explosion led to significant increases in gas prices in California, exacerbating the electricity crisis there. The U.S. National Transportation Safety Board subsequently determined that decades of inadequate testing and maintenance by the pipeline company caused the mishap.