A gas explosion is an accident resulting from ignition of a mixture of air and flammable gas, typically from a gas leak. In household accidents, the principal explosive gases are those used for heating or cooking purposes such as natural gas, methane, propane, butane. In industrial explosions many other gases, like hydrogen, as well as evaporated (gaseous) gasoline or ethanol play an important role. Industrial gas explosions can be prevented with the use of intrinsic safety barriers to prevent ignition. Lower and upper explosive limits Whether a mixture of air and gas is combustible depends on the air-to-fuel ratio. For each fuel, ignition occurs only within a certain range of concentration, known as the upper and lower flammability limits. For example, for methane and gasoline vapor, this range is 5-15% and 1.4-7.6% gas to air, respectively. An explosion can only occur when fuel concentration is within these limits. List of gas explosions 1900–1950 Australian federal MP George Edwards and a gas mechanic were killed on February 4, 1911, when a gasometer exploded on Edwards' property in Turramurra, New South Wales. The Pittsburgh gasometer explosion occurred during the morning of November 14, 1927 in the north side of Pittsburgh. A large gasometer exploded, killing 28 people and injuring hundreds. The Mather Mine disaster occurred on May 19, 1928 in Mather, Pennsylvania. A methane gas and dust explosion resulted in the deaths of 195 men. The New London School explosion occurred on March 18, 1937, when a natural gas leak caused an explosion, destroying the New London School of the city of New London, Texas. The disaster killed three hundred students and teachers. The Cleveland East Ohio Gas Explosion occurred on the afternoon of Friday, October 20, 1944. The resulting gas leak, explosion and fires killed 130 people and destroyed a one-square-mile area on Cleveland, Ohio’s east side. 1950–2000 On October 31, 1963 Indiana State Fairgrounds Coliseum gas explosion (later known as the Pepsi Coliseum) occurred during the opening night for the Holiday on Ice show, killing 81 and injuring nearly 400. The cause was an explosion following a propane tank leak. LaSalle Heights Disaster March 1, 1965. Gas line fractured in a low-cost residential neighborhood near Montreal, Quebec, killing 28 people and injuring 39. Reading, Pennsylvania, January 9, 1968. An explosion killed nine persons and demolished two houses. A gas company spokesman said Reading workmen digging in the street to repair