The mine was worked by driving headings east and west to the limit of the colliery and then the coal was extracted on a retreating wall basis. The coal north of the shafts had already been worked out (apart from a pillar to support the shafts and workings). South of the shafts the coal had largely been worked out back to the supporting pillar for about of the distance, that to the south was being actively worked at the time of the explosion. Headings were labelled numbers 1 and 2 east and west in the worked section, number 3 east and west and number 4 west in the southern extremity. The large areas to the east and the west of the central roads formed a large area known as the goaf. This space (up to across) was in part supported by pack walls and partially filled with waste. It was allowed to gradually subside, crushing the pack walls down. To prevent subsidence beneath Agecroft Hall, a pillar of coal about square had been left some beyond the limit of the 1885 workings. In the goaf the roof broke away from the Trencherbone rock resulting in voids forming above the low grade coal.