Chemical plants are a complex network of pipes which carry materials, often dissolved in organic solvents, from one process to the next. Valves control these movements.

Shell have a large refinery and chemical manufacturing plant in Ellesmere Port, Cheshire. They undertook a policy of leak detection and reduction. Operators check every valve in the Ethylbenzene unit with portable flame ionisation detectors. If leaks of volatile organic compounds (VOC's) are detected above 10,000 parts per million, then the valve is tightened or repaired until it falls below this threshold.

Shell have reduced their emissions of VOC's by 90% over the first three years of the programme and it has also led to a reduction in the amount of organic solvents used. This saves an estimated £17,000 per year.