Determining the time to re-enter an underground mine after a blast stoppage or development depends on several factors, including the air quality in the area. It is essential to use an air quality monitoring system that includes underground sensors to measure the concentration of harmful gases such as carbon monoxide (CO), carbon dioxide (CO2), and other pollutants. Based on the collected data, the appropriate time for safe re-entry can be determined.

Other risks should also be considered, such as the likelihood of rock falls or blasting events, which may require additional assessment.

Please ensure to verify important information from reliable sources.

Thanks for your reply Ali Al.Qassab . How do we decide the likelihood of rockfalls we decide? Is there any special method for re-entry protocol to decide such rock falls?

Usually the information on the stability of the rocks is studied by drilling and studying the core. Special attention is paid on fractures and faults. If the above are plentiful, the rocks after the blast may cave. The miners get familiar with the rocks very fast and get better at predicting caving events than visiting engineers/geologists.