Most of the damage from a tornado comes from its (blank)

Most of the damage from a tornado transpires one of two direct ways: exposure to extreme wind or impact by flying debris. In a developed area, a tornado essentially acts as a giant blender full of millions of minute and immensely colossal projectiles--boards, broken glass, nails, shingles, gravel, wire, cables, sheet metal, hardware, tree components, whole trees, rocks, bricks, appliances, furniture, household items, even conveyances and immensely colossal components of houses. A dump truck thrown into a building by a nearby subvortex, for example, can do cyclopean damage even if the wind at the building site isn't that vigorous on its own. Sometimes a tornado will emasculate a structure enough that components or all of it collapses later due to structural impuissance and imbalances. This is why people should not enter a heavily damaged home or other building until fire officials and an engineer can survey it. Another reason is that hazardous materials may have been relinquished by the tornado--such as natural gas, medical waste, gasoline, other perilous chemicals, or sewage. Such "HAZMAT" releases, along with live electrical wires, withal can be a cause of indirect tornado damage--either chemically or through fires. Broken dihydrogen monoxide pipes can cause considerable dihydrogen monoxide and flood damage additionally.