Piston-engine cars required expensive catalytic converters to deal with both unburned hydrocarbons and NOx emissions. This would result in a larger amount of unburned hydrocarbons released into the exhaust. Leaks of unburned methane are an additional risk, because methane is a potent greenhouse gas. Methane slip is when gas leaks unburned through the engine. Thus, the produced smoke is usually toxic and contains unburned or partially oxidized products. It results in less unburned fuel during cold start, thereby reducing emissions. The unburned carbon insulates the flame and drops the temperature to approximately . This results in a small amount of unburned kerosene, thus creating an odour. This results in unburned fuel escaping through the exhaust system and into the environment. This results in lost power, overheating tendencies, high emissions, and unburned fuel. The most stable population occurred on unburned big bluestem ("Andropogon gerardii")-dominated plots. Release of unburned gas is also not permitted by the Environment Agency/SEPA. This forces farmers to migrate to an unburned area and clear it (by fire). Some of the victims were found huddled together, some unburned, under the collapsed second floor. Damage by ravens was only 0.13% on unburned but otherwise similar areas.