Which signs indicate a spontaneous combustion risk (Spon Com) in underground conditions?

• A. Increase in carbon monoxide; sweating; increased heat; haze; benzene smell; smoke or fire.
• B. Decrease in carbon monoxide.
• C. Nosebleeds.
• D. Water spray.

Answer: (A)

Spontaneous combustion in underground coal mining happens when coal oxidizes and releases heat faster than it can be dissipated. When this oxidation ramps up, you’ll see a combination of signs: an increase in carbon monoxide from the oxidation process, the atmosphere feeling hotter and people or equipment sweating more, and a haze or smoke-related appearance as gases build up. A distinctive smell, such as benzene, can occur due to volatile compounds released during coal oxidation. If the process progresses toward ignition, actual smoke or fire becomes evident. These signs collectively point to a rising risk of spontaneous combustion and the need for immediate cooling, ventilation adjustment, or other mitigation. In contrast, a decrease in CO, nosebleeds, or using water spray are not indicators of Spon Com risk by themselves; water spray is a response to control heat and gas, not an alert sign.