Acting Palo Alto Fire Marshal Gordon Simpkinson said corrosive action of soil can lead to leaks in 50- or 60-year-old gas lines.
"If (homeowners) don't take care of it, it could reach the point where it causes a problem similar to what happened on Maureen," Simpkinson said, adding that, if residents smell gas, the Utilities Department has a program to inspect homes free of charge.
Before their Maureen Avenue house literally exploded last September, Andrew and Yvonne Ware had consulted with their furnace installer about a natural gas-like odor.
The installer, from the now defunct Dahl Plumbing, did not smell natural gas and told the couple the odor probably emanated from a dirty-diaper pail, the Wares told fire inspectors.
On Sept. 30, Andrew Ware was finishing up his morning shower when he heard a big boom and saw smoke, flames — and blue sky where his bathroom roof had been. He escaped the burning home through a bathroom window. Yvonne Ware already had left to take the couple's child to day care.
Investigators determined the fire had been fueled by a gas leak.
"That's the only thing that can lift the roof of a house like that," Simpkinson said.
However, inspectors listed the fire as "undetermined" in their final report because they were unable to pinpoint precisely the source of ignition.
They speculated it could have been a water heater cycling on to supply hot water during the shower. Another possible cause could have been the thermostat of a wall furnace.
Inspectors estimated property loss to be $375,000 in the Maureen Avenue fire, with another $100,000 in contents loss.
The fire, which quickly consumed most of the house, could be seen from the sixth floor of City Hall, more than 3 miles away.
For residents concerned about possible gas leaks, Simpkinson said, "If somebody's got something where they occasionally smell it, they're not quite sure, they can call the Utilities Department and they will come out with gas-detection equipment and go through the house room-by-room. This is free of charge to the homeowner."
However, if residents notice a strong smell of gas, they should call 911 so the fire department can immediately come and turn off the gas, Simpkinson advised.
For easier repair, leaky underground gas lines can be disconnected, capped off and re-routed through garages or walls, he said.