What is the incombustible material content for mine roadway dust within 200 m outbye the last completed line of panel cut-throughs?

• A. 70%
• B. 80%
• C. 85%
• D. 90%

Answer: (C)

The key idea is that dust must contain a high enough proportion of noncombustible material to suppress explosion risk. Incombustible content is the percentage of dust that is inert (noncombustible) by weight. For roadway dust within 200 m outbye the last completed line of panel cut-throughs, the regulatory requirement is a minimum of 85% incombustible content. This higher inert content helps dilute and cool any coal dust that could become airborne, making flame propagation less likely if ignition occurs. Measurements are done by sampling the dust and analyzing the noncombustible portion in the lab. So the best answer is 85%.