To explore the sustainability of urban utility tunnel and the possibility for methane/hydrogen mixture transportation, FLACS, the gas explosion simulation software, was used to study the explosion in gas compartment in utility tunnel, and the fuel are 100%CH4, 90%CH4+10% H-2, 80%CH4+20% H-2 respectively. The results show that with the increase of proportion of H-2, vapour cloud with same volume leads to higher overpressure, which increase 16% averagely in 10% H-2 and 32% in 20% H-2; but in long-narrow structure confined space, the length and the height of vapour cloud affect more than the total mass of fuel; the ventilation opening and door can prevent the fire transfer but can prevent the shock wave and control overpressure; for the situation that ignition position is closed the firefighting wall, if the fuel is enough, the peak overpressure shows at the wall rather than other closed position form the ignition position, so the firefighting wall should be reinforced; for people in utility tunnel, they will not be hurt by shock wave but by fire because of the board range, so the risk of burn exists that people must leave compartment immediately. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.