Moura is one of the small rural towns in the Shire of Banana, which is 150km south-west of Gladstone in Central Queensland, Australia. Moura becomes well known after the three major mine underground explosion accidents occurred in 1975 Kianga No.1, 1986 Moura No.4 and 1994 Moura No.2 (Queensland University, 2019). Moura No.2 mine is an underground coal mine which is operated by BHP Company (Hagemann, 2016). Moura No.2 mine started in 1970 and 170 people employed and annual out put varied 550,000 and 650,000 tonnes of raw coal, which come from two continuous miner production units.

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On the 7th August 1994 at about 11:30 pm, mine explosion at Moura No.2 took the life of eleven mine worker. During the mine accident, twenty-one workers working at the underground at that time and only ten coal miners make it back to the surface. Unfortunately, the eleven coal miners were failed to return to the surface. These workers were working for the first pillar development in the south section of the mine, which is 265 meters underground and 3 kilometers away from the mine entrance. After the first exploration, another exploration was occurred at 12:20 on 9th August 1994. Therefore, rescue and recovery attempts were abandoned and closed the underground mine. That was a significant loss for the community (Ellicott, Roxborough, Windridge, Neilson, & Parkin, 2019).

Figure 1 Moura No.2 Underground Coal Mine
Retrieved from: https://me.cfmeu.org.au/news/moura-no2-anniversary-1994-disaster
Moura mine was equipped with several preventive measures from explosion. These controls can be named as effective methane drainage without the application of a vacuum, strata control, ventilation, gas monitoring, radio communication, emergency response team and personal protective equipment. All these measures were not able to eliminate the hazard completely, but few of them were crucial in reduction, isolation, deviations and maintaining the hazard prior to the event (Ellicott, Roxborough, Windridge, Neilson, & Parkin, 2019).

A proper ventilation system was in placed with air entering from four portal. Two proper centrifugal exhaust fans were placed and designed to meet safety requirements if any explosion happened. The purpose of ventilation was to cool the temperature down and provides airflow in underground environment. Safety measures in the ventilation system can be summaries as below:

The fans were attached to a shaft by steel ducting with two explosion pressure relief panels in order to keep the whole system safe in case an explosion occurs (Engineering design control).
A backup diesel powered alternator was installed to start automatically in case of power failure (Engineering design control).
Operational alarms and ventilation pressure monitoring at the main fans were relayed back to the mine office monitoring station (Administrative control).
There were main ventilation splits to direct and return air separately (Engineering design control).
Re-entry (Engineering design control) (Ellicott, Roxborough, Windridge, Neilson, & Parkin, 2019).

The Moura mine had several gas monitoring systems in place. These monitoring systems can be named as, Maihak Unor system with CAMGAS (Computer Assisted Mine Gas Analysis), use of on-site chromatograph which was provided by SIMTARS (Safety in Mines Testing and Research Station) laboratories and on-site hand held MSA Minder (Portable Gas Detectors).
The Maihak Unor system was detecting hazardous gases such as methane and carbon monoxide.  Concentration of these gases was determined by analysing of 12 tube sample gas and with the aid of CAMGAS (Computer Assisted Mine Gas Analysis) continuously. CAMGAS was comparing the results against pre-set values. The display color was changing from green to red if the gas concentration was exceeding the alarm pre-set level and subsequently loud siren was sounded by the system outside of control station.
Use of MSA Minder Portable Gas Detector was another tool to detect methane and carbon monoxide gas level in mine. These portable monitoring devices were carried by mine officials regularly. Finally, use of chromatograph in a close examination in areas prior to sealing was another precautionary measure(Ellicott, Roxborough, Windridge, Neilson, & Parkin, 2019).

The origin of Moura No.2 underground mine explosion occurred at the 512 Panel of the mine and the cause of failure is over heating of coal in that panel. The panel is where the eleven coal miners undertaking for the first pillar development. The over heating is cause after the 512 panel was sealed and the methane gas was trapped and cause the immediate explosion. The causes to first explosion were (Ellicott, Roxborough, Windridge, Neilson, & Parkin, 2019).

Lack of communication between the team

The ignorance on the presence of high temperature, carbon monoxide gas existence and not enough fresh air for the underground working area
Failure to withdraw persons from the mine while the potential existed for an explosion.
Failure to use the gas chromatograph equipment to detect the CO limit.

The mine management failed to maintain, communication and reporting system. The second explosion is stronger than the first explosion. The large amount of dust, smoke, carbon monoxide and some other gases were emitted to the surface. Carbon monoxide level is rose to over 400ppm, therefore every miner from the surface need to use self-rescuer and immediate evacuate to the safe place(Ellicott, Roxborough, Windridge, Neilson, & Parkin, 2019).
References

Ellicott, C. W., Roxborough, F. F., Windridge, F. W., Neilson, P. J., & Parkin, R. J. (2019). Moura No. 2 underground mine accident: report of the Warden’s inquiry Retrieved from https://publications.qld.gov.au/dataset/moura-mining-disaster-inquiry-reports/resource/a8e96409-52a3-4075-b4a6-b1224ecc8e63
Hagemann, B. (2016). Moura memorial snubbed by mining companies – Australian Mining. Retrieved from https://www.australianmining.com.au/news/moura-memorial-snubbed-by-mining-companies/
Queensland University. (2019). Moura,Queensland Places. Retrieved from https://www.queenslandplaces.com.au/moura