Which of the following is NOT a typical sign of spontaneous combustion risk?

• A. Decrease in haze.
• B. Increase in carbon monoxide.
• C. Increased heat.
• D. Benzene smell.

Answer: (A)

Spontaneous combustion risk comes from coal self-heating: as oxidation accelerates, heat rises and gases are released. You’d expect to see higher temperatures and more gases like carbon monoxide, plus VOCs such as benzene, which can produce an odor. Haze or visibility issues typically worsen as smoke and fumes accumulate. A decrease in haze would not be expected as a sign of risk. So the signs you’d look for are increasing heat, rising carbon monoxide, and a benzene odor, not a reduction in haze.