That was the situation simulated for the workers and assessed by safety authorities for the Queensland Level 1 Emergency Exercise held on Monday July 30.

Assessors from Simtars, the Construction, Forestry, Mining and Energy Union, Minerals Industry Safety and Health Centre and the Queensland Mines Rescue Service converged on Grasstree at 8pm and sprung the exercise on mine employees in a bid to test safety procedures and equipment at the mine.

The situation increased in severity as mine workers were forced to deal with not only the gas explosion and the loss of ventilation in the tailgate short-circuiting the air and allowing the gas fringe to come forward but also injuries and loss of equipment use.

Man-riding at the No. 1 shaft was temporarily inoperable, communications were initially lost and the longwall crew, particularly those in and around the shearer, suffered a multitude of injuries.

Three crew members were then identified as being unable to self-escape and required external assistance from the QMRS.

Simtars acting director Paul Harrison said assessors focused on self-escape procedures including the changeover of self-contained self-rescuers, the use of changeover bays, the incident management team process, QMRS response and underground deployment, as well as the emergency call-out procedures of the minesite and the Department of Mines and Energy.

Harrison said overall the exercise was a credit to the mine and said the mine's application of Mine Emergency Management System was very effective.

Last year's Level 1 exercise at Broadmeadow Mine identified the incident management response as being of concern, with Simtars recommending each site ensure staff are trained, practised and competent in their role in the event of an emergency.

Harrison said the use of non-verbal communication by workers after they lost their ability to speak through the use of their SCSR worked well during the drill, as did the use of vehicles for escape.

Harrison said the donning and changeover of SCSRs continues to be an issue as well as first response or inseam response problems.

All mine crews and emergency teams were de-briefed after the drill and a report on the exercise, including Simtars recommendations, will be released in October.

Harrison said next year's Level 1 exercise will be at Newlands underground coal mine, although exact timing and the scenario will be a closely guarded secret until that time.

Keep watching International Longwall News for the outcomes of the Grasstree exercise.