A chemical explosion starts pressure waves in themedium where it happens. Explosions are categorized as deflagrations if the pressure waves aresubsonic anddetonations if they aresupersonic. When a detonation happens, the resulting pressure waves are namedshock waves.
Unintentional explosions can be caused when chemicals are mixed together, or when pressurized containers or flammable materials are heated or exposed to flames. To cause an explosion, pressure does not have to be present but is always a result of an explosion.
Several safety measures are used to prevent unintentional explosions. Many countries require that chemicals, fuels, and pressurized containers that may explode be labelled with warning labels. As well, many countries have regulations restricting the possession and use of potentiallyexplosive materials so they will only go to appropriate industrial and research uses. Transportation regulations require potentially explosive chemicals, fuels, and pressurized containers to be transported safely.
Intentional explosions are caused when armies fireartillery or whenair forces dropbombs on enemies.Military engineers handle explosives and arrange intentional explosions during wartime. Intentional explosions are also used by civilians indemolition. They break up old and obsoletebuildings andbridges, and break rock and stone for construction. Explosions are made for activities such asmining, construction, and large-scalecivil engineering projects such as building tunnels, roads, railways, and dams.
