Where is the most appropriate specific location to take a bag sample from an open goaf?

Taking a bag sample from the goaf stream in the tailgate at the diurnal low is the most appropriate specific location due to several factors related to gas behavior and concentration levels in mine atmospheres.

The goaf represents an area where the roof has collapsed, and it is a zone where gases can accumulate. Sampling during the diurnal low, which is the period of lowest gas concentration and activity related to changes in temperature and atmospheric pressure, allows for a more accurate representation of the gas composition present in the goaf. This timing reduces the influence of disturbances that can occur during peak operations when the mining activity is more intense, potentially leading to misleading results.

Moreover, collecting samples in the tailgate area, where airflow typically slows down, enhances the ability to capture the gases released from the goaf. This location is crucial for assessing the ventilation effectiveness and understanding the potential hazard levels, as it provides insights into how gases migrate and concentrate in abandoned areas of the mine.

This thoughtful consideration of timing and location maximizes the reliability of the sampling process, ensuring that the data collected accurately reflects the gas conditions in the mine environment.