Accidents like the one in San Bruno are rare but they are not unheard of. Two years ago a man was killed in Sacramento when a Pacific Gas and Electric pipe started leaking and exploded. Earlier this year a massive blast in South Los Angeles killed one person and injured another.
"Every household has natural gas. That means that on every street there must be a natural gas pipe, so it can happen to any neighborhood in this country," warned USC Engineering Professor Fokion Egolfopoulos, who specializes in the combustion of fuels.
He said when natural gas escaped the 30-inch gas line in San Bruno, just a small spark would have been enough to ignite it and set off that massive blast. He explained the number of gas lines in San Bruno is likely no different than anywhere else.
That's where detecting a leaky pipe and turning it off can mean all the difference.
"If you have a good sense of smell you can smell it quite readily," said L.A. City Fire Capt. Jaime Moore, who is trained to deal with gas leaks. "First thing to do is evacuate the area, open the windows and then notify either the fire department or your natural gas provider."
He said all homeowners should know where their gas turnoff valves are located and make sure none of their gas-powered appliances are leaking. Fire officials said only to turn off gas valves if instructed by your natural gas company or emergency workers. Once gas is turned off, only your company should turn it back on.