Regan on portable gas monitors

Relying too much on handheld gas monitors can be fatal. ILN talks to NSW chief inspector of coal mines Rob Regan.
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Blair Price

In July Regan issued a safety alert to make mine operators aware of the capabilities and limitations of portable gas testing equipment.

Two separate incidents in the state fuelled this action.

One was when an undermanager felt dizzy after carrying out an inspection of pillar panel return.

It seems he entered an oxygen-deficient atmosphere faster than his PGM could react.

The other incident was when two deputies inspected a face road after a large amount of methane was released.

They got a reading of 2% and subsequently retreated to a safe location.

But when they checked the readings again they found oxygen levels peaked at 7.5% and 8.4% on their handheld monitors.

While the methane levels might have been depressed by the low oxygen environment, those oxygen levels could have rendered the deputies unconscious.

Consequently it was assumed the oxygen levels on the devices were not representative of the atmosphere in the breathing zones of the deputies.

A subsequent investigation at the mine revealed that a monitor took 6 seconds to detect 1% methane and 29 seconds to detect 2% methane.

The Australian standards allow 30 seconds for a methane response from these devices and 60 seconds for toxic gas and oxygen sensors.

But given that it’s possible to walk 1 metre per second, minesites were reminded about the hazards of relying too much on handheld detectors.

“It should be well known that they are not instantaneous detectors,” Regan told ILN.

“Care still has to be exercised when you are using them to move into any atmosphere.”

He said the alert was designed to reinforce the response times and the need to train and refresh staff that use them on a regular basis but “might fall into the trap of thinking that they are actually instantaneous”

“None of the gas monitoring is actually instantaneous because there is always a period of time where it has to process the gas sample.”

Improving response times

But the state’s mine safety unit also called for PGM manufacturers to review designs to improve response times.

One major manufacturer has stepped up to the challenge with Regan expecting an Industry & Investment NSW mine safety report on its handheld device to be ready by the end of February or early March.

He suspected the manufacturer was already well advanced in designing this new breed of monitor before the safety incidents with this type of equipment this year.

Other rival suppliers are expected to step up to the plate once this manufacturer brings an approved, fast-response handheld gas monitor to the market.

Regan would like a PGM capable of response times within 5-10 seconds for whatever gas a miner is looking for, especially if it is used for on-the-spot inspections by deputies, under-managers and ventilation officers.

He said this equipment does exist.

“Operators really need to look at the performance specification for the equipment because they should realise that the type of work that they want carried out with this is work that you want the response time in the single digits of seconds,” he said.

He understands the difficulties with designing PGMs which provide accurate responses at an even faster rate.

“The chemistry of measuring gases is limited by a fairly fixed set of gas properties and conditions, and the way in which they can actually improve on that will take some pretty interesting thinking to be able to come up with different techniques to speed up the response times.”

But he is throwing the challenge out to other manufacturers of these devices to make progress on this front.

“You can get these situations where a faster response time would give a greater safety for the people who are doing the inspections, so put your thinking caps on.”