Very little research has been conducted to date to try and establish safe and productive post detonation re-entry times, despite the importance it has on health, safety and production in Australian metalliferous mines. Many incidents and accidents occur each year due to over exposure of personnel to blast fumes and there are significant losses in production due to poor procedures for determining appropriate re-entry times after blasting. The aims of this thesis have been to examine approaches to determine suitable re-entry time to improve safety and production at the Cannington mine.
A literature review has highlighted a number of important aspects of previous research, namely mathematical modelling of blast fume decay, exposure standards and recent test work on blasting fumes and re-entry times. A simulated case study has demonstrated that blast re-entry times could probably be based on concentrations well in excess of the conservative TLV8hr and TLV12hr. The TLV8hr has however been adopted for determining re-entry times in this study.
Cannington currently bases their re-entry times on the experience of their workforce and have not in the past performed any testing or attempted to apply any other means to determine safe and productive re-entry times. A statutory body has cautioned the use of experience alone, and en element of risk exists for Cannington with the potential for the overexposure of personnel and losses in productivity due to inappropriate methods for determining re-entry times.
Portable gas monitoring equipment and the Citect Mine Monitoring system have been used to capture the behaviour of blast gases in auxiliary ventilated level development headings at Cannington. The portable instruments, calibrated to international standards, have been used to verify the accuracy of one another and that of Citect to be within about 10ppm, 1ppm and 0.5ppm for carbon monoxide, nitric oxide and nitrogen dioxide respectively.