 Other hazardous materials such as mercury, and sodium azide (the propellant used in air bags) may also be removed.After all of the parts and products inside are removed, the remaining shell of the vehicle is sometimes subject to further processing, which includes removal of the air conditioner evaporator and heater core, and wiring harnesses.The remaining shell is then crushed flat, or cubed, to facilitate economical transportation in bulk to an industrial shredder or hammer mill, where the vehicles are further reduced to fist-sized chunks of metal.