Biogas forming in sewers via anaerobic digestion can be a potentially foul-smelling and explosive hazard (chiefly due to chemical spills).
Many of these lamps were installed in the UK in towns and cities including Sheffield, Winchester, Durham, Whitley Bay, Monkseaton and Blyth, Northumberland.
The flame in the lamp does not actually generate sufficient thermal energy to combust any of the odour compounds in the air.
In 2016 Sheffield residents campaigned for the lamps to be restored when the city council's replacement of every lamppost began, as part of the 25-year Streets Ahead road improvement programme.
[citation needed] If the methane concentration were over the explosive limit (≈ 50,000 ppmv) the open flames in the lamps would burn like flares.