Trencherbone was worked with candles. Prior to the day shift the firemen tested and marked up those areas free of gas. The men were then allowed to proceed to their various workplaces, but only using safety lamps. The firemen made another round and if all was well would light the men's candles after which naked lights were permitted. Once candles had been lit men were allowed to smoke. Officially no pipe or tobacco were meant to be present when naked lights were prohibited (rule 33), but in practice the men had them in their pockets, along with matches, prior to the second visit.