It has responded to a US Mine Safety and Health Administration report into the causes of the Sago Mine explosion, which found the possibility of a lightning strike to sealed goaves or mined out areas must be considered as a direct ignition source.

Lightning can also indirectly couple to insulated conductors in a sealed area and such coupling would have sufficient magnitude to generate an arc capable of igniting an explosive mixture of methane.

The obligation on those who seal goaves or mined out areas is to apply new, proven, practical technology to reduce the risk to mine workers from an explosion after sealing, the inspectorate said.

“Coal operators are to consider indirect coupling of lightning into sealed areas as an ignition source when determining the risk of explosions and apply new, proven, practical technology to control the risk of explosions,” it said.

“Coal operators are advised to remove all conductive material that may be insulated from the general mass of earth from goaf areas and areas that are to be sealed.”

Where conductive material is likely to remain in sealed areas, for example windblast monitoring or gas monitoring, then it can only be done where the risk is as low as reasonably possible.

Coal operators are advised to develop and implement a gas monitoring regime designed to specify the placement of sampling points and sampling frequency for pre and post sealing times. The gas monitoring regime shall be developed in consultation with the mine’s inspector of coal mines.

They are also advised to develop the capability to remotely monitor sealed areas from the surface for times when the mine has been evacuated.

The structural rating of 20 and 120 psi seals should be to a standard acceptable to the chief inspector of coal mines. The structural rating of 20 and 120 psi seals should extend beyond the seal matrix and is to include the junction of the seal matrix with the roof, ribs and floor at the seal location.

“It is recommended that practical, regular training in the donning, use and change-over of self-rescuers be adopted in NSW,” the inspectorate said.

“This training should be undertaken at a frequency that ensures employees are fully familiar with the self-rescuers in use at the underground coal mine.

“This training should be included in the Emergency Management System required by the NSW Coal Mine Health & Safety Act and Regulation.”