Opinion ID: 1345745
Heading Depth: 1
Heading Rank: 12

Heading: Gasoline as an explosive.

Text: The expert witnesses agreed, however, that explosions are not all caused by explosives as that term is understood in the scientific community and used in the relevant statutes. Not every substance or object that is capable of exploding is an explosive. [6] The expert testimony in this case established that neither gasoline nor gasoline vapor is an explosive. The People's arson experts testified that gasoline does not burn below a temperature of 495° Fahrenheit. It vaporizes at -45° , however, and the vapor will burn when it is within the flammable range of 1.4 to 7.6 percent of the air. When the combination of air and vapor ignites, a relatively instantaneous flash burn occurs, a sudden oxidation or burning of the flammable gasoline vapor. That flash burn stops as soon as the flammable mixture is consumed, and does not cause any further fire unless other combustible material is ignited during this process. A flash burn does, however, rapidly heat the ambient air. The heated air expands, and that expansion of existing gases causes a sudden increase in air pressure. This increased pressure normally dissipates into the surrounding air space, but if the heated and expanding air is confined in a container, the pressure continues to increase. If that pressure exceeds the structural strength of the container, the resulting overpressure will cause the container to explode. Whether a flash burn, such as that occurring when a combination of gasoline vapor and air is ignited, will cause this type of explosion depends primarily on (1) the amount of flammable vapor-air mixture present at the moment of ignition, and (2) the size of the container. One expert explained: The quantity of the fuel-air mixture [necessary to cause an explosion] is directly related to the cubic feet of the container. If the quantity of flammable mixture is too small or the container is too large, the resulting pressure will be insufficient to cause the container to explode. Moreover, the effect of an explosion caused by the overpressure effect of a flash burn differs greatly from that of an explosion caused by what were described by the experts as true or high explosives. The source of a concentrated explosion, one caused by a true explosive, is typically a small quantity of an explosive solid material such as a stick of dynamite. A concentrated explosion is self-contained  independent of ambient conditions, and not dependent on a supply of oxygen. When detonated the explosive material undergoes a chemical reaction that abruptly generates a large quantity of gas, mainly nitrogen, that was not present before the detonation. The volume of gas rapidly becomes thousands of times larger than that of the original solid, and the resulting shock wave creates a compressive force of approximately 25,000 pounds per square inch. By contrast, an explosion caused by a flash burn of gasoline vapor and air is diffuse. Its source is not a single piece of explosive solid material, but the entire flammable mixture of gases in the air. Such an explosion is entirely dependent on the ambient conditions. If any is lacking, e.g., insufficient time for the gasoline to vaporize or for the vapor to mix with the air, a vapor-air mixture that is too rich or too lean, or a container that is too large at the time of ignition, there will be no flash burn or, if one occurs, no overpressure and no explosion.