THE NSW Department of Primary Industries has released a mine safety alert regarding the response times of portable gas monitors.
According to the NSW DPI, there have been two incidents at NSW underground mines where mining officials have been exposed to potentially dangerous environments due to a delay in response times of hand-held gas monitors.
In one instance, an Undermanager entered an oxygen-deficient atmosphere at a quicker rate than his gas monitor could react.
In another incident, two deputies were inspecting a face road after the release of a large amount of methane. Focused on detecting the methane, upon their return to a safe area, they found the oxygen “peaks” on the gas monitors were 7.5% and 8.4%.
According to the DPI, the methane readings may have been depressed by the low oxygen environment.
An investigation by the DPI found a monitor at one of the collieries had a six-second response time for 1% methane, and a 29 second respond time for 2% methane levels.
Australian Standard AS/NZS 60079.29.1 allow a response time of 30 seconds for methane, and 60 seconds for toxic gas and oxygen sensors under AS/NZS 4641.
The DPI says given workers can walk at one metre per second, people can proceed into a rapidly deteriorating environment without recognising the hazards.
Additionally, normal alarm systems on gas monitors have only one alarm. This cannot be reset. When dealing with changing environments, a mining official may not notice a change in another of the gases being analysed, leading to a lack of action on their part.
Mines should identify the response times for each gas for all types of gas monitors in use, train all personnel accordingly, and determine a protocol for mining officials to use when carrying out an inspection after the first alarm has initiated.