What indicates the effectiveness of ventilation in mining?

The effectiveness of ventilation in a mining operation is most accurately indicated by the volume of air passing through the last crosscut. Proper ventilation is crucial for maintaining air quality, controlling temperature, and ensuring that harmful gases and dust are adequately diluted and removed from the mine atmosphere.

Monitoring the volume of air is essential because it directly correlates with the flow rate and circulation of air throughout the mine. Adequate airflow is necessary to ensure that workers are provided with enough fresh air to breathe and that hazardous conditions are mitigated.

Factors such as the temperature in the mine, the number of entries, and the number of workers can provide some contextual information about the environment and its general safety; however, they do not directly measure how well air is being circulated and replaced. Therefore, the volume of air passing through the last crosscut serves as a clear and quantifiable measure of ventilation effectiveness, making it the correct choice.