Extinguishing tire fires is difficult. The fire releases a dark, thick smoke that contains cyanide, carbon monoxide, sulfur dioxide, and products of butadiene and styrene. Burning tires are heated, and, as they have a low thermal conductivity, they are difficult to cool down. Moreover, they frequently burn inside even if they are extinguished from outside, and easily reignite when hot. One possible remedy is to cover the fire with sand, reducing the supply of oxygen and the exhaust of smoke. After extinguishing and cooling down (which may last several days), toxic chemicals can be neutralized.[2]