A natural first step in the fire protection of buildings and their occupants is to prevent fires from starting. Building codes and zoning ordinances regulate the combustibility of the materials with which buildings may be built in different areas of a city, as well as the conditions under which flammable and explosive substances may be stored in or near buildings. Proper building maintenance ensures that rubbish does not pile up anywhere. Firefighters and fire under writers (insurers) inspect buildings periodically to find whether any unsafe concentrations of combustible materials have accumulated in them. Through these same means—codes, zoning ordinances, maintenance, and inspection—potential sources of accidental ignition are eliminated. Heating devices, chimneys, electrical systems, electrical devices, and hazardous industrial processes are especially stringently controlled. Smoking is prohibited by law in gasoline stations, certain types of industrial plants, auditoriums, and many public buildings.
Lightning can damage and set fire to buildings in exposed locations. A lightning bolt is the instantaneous release of a very high electrical potential between a rain cloud and the earth. Pointed metal rods connected directly to the earth through heavy, highly conductive cables furnish lightning protection for buildings (see ill. 3 below). By leaking an electric charge from the ground off their points, the rods are often able to neutralize the electrical charges of clouds before lightning bolts form. If lightning strikes the building, the rods and conductors offer a path to the ground of considerably less resistance than the building itself. Thus they attract the lightning away from the fabric of the building and conduct it safely to the ground.
ill. 3: Conductor and ground rod shown in lightning-resistant building
structure.
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