The DOT regulation at 49 CFR 174.450 previously stipulated that when fire occurs in a domestic rail shipment of charcoal in transit, water should not be used if it is practicable to locate and remove the burning charcoal. Any charcoal that becomes wet whi

The DOT regulation at 49 CFR 174.450 previously stipulated that when fire occurs in a domestic rail shipment of charcoal in transit, water should not be used if it is practicable to locate and remove the burning charcoal. Any charcoal that becomes wet while a fire is being extinguished must be removed from the car and not reshipped, and the remaining charcoal must be held under observation in a dry place for at least 5 days before forwarding. What is the most likely reason DOT regulates the domestic transportation of charcoal in this fashion? What chemical reaction is involved here?