The level one emergency exercise, held at the Newlands longwall mine in Queensland in November 2000, was a turning point for the coal mining industry. Not only did the exercise thoroughly test the mine’s emergency preparedness, and generate important lessons for the rest of the industry, it was also the first real opportunity to evaluate the application of compressed air breathing apparatus (CABA).

Since then, the underground coal industry has embraced the new technology, with some 900 CABA units sold into the industry or on tender, primarily in New South Wales. Unusually, the drive towards CABA has not been legislatively motivated but is the result of changing philosophies towards mine emergencies.

Chairman of the Newlands emergency exercise management committee, and senior inspector of mines, Queensland Department Natural Resources & Mines (DNRM), Greg Rowan, describes the exercise as a watershed for the industry.

One of the key findings to emerge from the testing, Rowan says, was that CABA added a “powerful weapon to the armory of the self-escape philosophy. Its flexibility, ease of use and ability to facilitate communication makes it well suited to the cause of emergency response, particularly as it provides a rapid, in-seam first response capability.”

The response to the 1994 Moura No.2 disaster had shifted the emphasis from traditional search rescue to self-escape, underpinned by aided surface rescue by trained brigades. The new focus was to equip workers underground with the facilities, equipment and training to get themselves out, reflecting the awful statistic that in community-wide rescue situations, 49% of the fatalities are made up of rescuers.

Another outcome of the Moura No.2 inquiry was legislation governing the appropriate safety equipment a mine had to supply to its workers.

In 1997, the Queensland mines department withdrew approvals for the old style filtered self rescuers (FSRs), leaving only newer, self contained self rescuers (SCSRs) as the sanctioned system in the state.

The differences between FSRs and SCSRs are well known. Anyone who has ever undergone induction prior to entering a NSW longwall mine will recall being warned of third degree throat burns in the eventuality of having to wear an FSR. Another drawback to the FSRs is that they don’t protect against oxygen deficient atmospheres.

SCRSs have their own oxygen supply but have other problems, including variations in rated and actual duration, the inability of wearers to communicate, and no reading of remaining oxygen.

An escape system based on SCSRs only caters for self-escape within a limited timeframe of oxygen.

According to chief executive officer of the NSW Mines Rescue Service (MRS), Murray Bird, USA studies suggest that during every changeover process from one SCSR to another, one person in 10 will breath in instead of out (and potentially die). This was based on studies of mine workers who had been trained within the past few months.

The withdrawal of approvals for filtered rescuers compelled Queensland mines to take the step up to the next level of technology, while NSW mines, on the other hand, continued to operate with FSRs.

Under current Queensland legislation all underground workers are fitted with a belt-worn SCSR, usually of 30-minute duration. Caches containing longer duration (60- and 90-minute) units are located at a point reachable by all average workers. An ACARP project found factors such as body mass and heart rate impacted on the duration of SCSRs and indicated it should be estimated at 60% of the rated duration. This duration is reduced by another 60% if visibility is poor (less than a metre) and there is no guidance system available. Therefore sufficient SCSR units had to be made available to allow all people to escape from the mine, travelling by foot in reduced visibility conditions. Some mines have up to 300 units.

While Queensland mines were putting in place SCSR equipment and conducting risk assessments around them, the NSW MRS began looking into the next technology leap to CABA equipment. NSW mines are now leapfrogging their Queensland counterparts by going straight from FSR to CABA. About 80% of NSW mines are currently implementing some CABA capability, Bird said.

While bulkier than SCSRs, CABA technology has improved in recent years, with units offering durations of 60-100 minutes. But what brought CABA into contention in underground coal mines was the development of quick fill options in-seam, enabling personnel to quickly tap into large compressed air cylinders to refill their units without being exposed to the mine atmosphere.

The fact that CABAs can be refilled in-seam has changed thinking in ways that may not be fully appreciated. What hadn’t been possible before was the option for underground workers to respond in-seam to an evolving crisis. “The quicker rescue trained persons with breathing apparatus go active in the affected area the greater the chances of rescuing persons and/or extinguishing a fire,” Bird said.

In recent years there has been recognition that under conditions of extreme duress, complex human psychology affects decision-making. Numerous intrinsic and extrinsic objectives compete, such as fears of leaving colleagues behind and being the sole survivor versus following the dictum to self-escape at all costs.

According to DNRM’s Rowan, people cannot conform to the simple algorithmic instructions most mines teach: At the first sign of smoke, don your SR; proceed to crib room to wait for instructions, etc.

“These simple rules do not provide the complex interaction in circumstances that can exist during an emergency and certainly don’t allow for the decision-making processes of the people involved,” he said.

“Workers underground do not don their self rescuers at the first sign of smoke. They first try to work out what’s going on. From a simple algorithm you’ve got 100 decisions to make.”

There have been a number of cases where underground workers have attempted an aided escape or rescue and even fire fighting activity while relying on the protection of escape equipment (FSR or SCSR), Bird said. In other words, people make irrational decisions under duress and so, against that background, giving them access to the best equipment is the best emergency response strategy.

“If it is anticipated or expected that mine personnel would or should be involved in these types of actions then the appropriate equipment, systems and training must be provided,” MRS’s Bird said.

Of the three breathing apparatus mentioned, CABA is the only unit that can deliver coverage for all aspects of escape, in-seam intervention and rescue.

Introducing CABA involves a three-stage procedure. In stage one a mine has a number of CABA units integrated into the SCSR escape system but not enough for everyone. Stage two is a full CABA escape system with underground refill stations. And stage three is when CABA is integrated with rescue, permitting in-seam and surface based rescue.

Of NSW mines, most of the Powercoal operations, three Enex Resources mines and the BHP Billiton Illawarra mines have ordered enough CABA units to warrant stage two classification, Bird said. Training on stage three (in-seam intervention) will not be started until the self-escape systems are fully implemented and all employees are trained to a suitable level.

See the related table.