Stephen A. Renehan of Irvington still jumps when he hears a car backfire, the legacy of a day last month when a house blew up 17 doors away, knocking him to the ground.
In the weeks after the explosion, which killed the elderly woman who lived in the house, fears grew in the neighborhood that natural gas could leak in other homes. Investigators said the blast probably was caused by an appliance left on or by a leak, but they couldn't be sure because the explosion destroyed the evidence.
Last weekend, the Baltimore Gas and Electric Co. responded by inspecting 136 homes and telling residents how to minimize the potential dangers. Spokesman John Metzger said that minor adjustments were made to some appliances and that five service pipes leading to homes were replaced because of minor leaks.
Now, Mr. Renehan says, the neighborhood is starting to heal. "Slowly but surely, things are settling down."
Although natural gas explosions can be devastating, they are rare. BG&E officials say the last death involving a gas leak in the Baltimore area was 12 years ago.
Two years ago, an explosion in Forest Park destroyed an unoccupied house.
When they do happen, gas explosions heighten awareness of how dangerous gas can be, BG&E officials said.
Reports of gas odors went up 50 percent in the two days after the Irvington explosion, said Michael E. Griffin, manager of BG&E's customer service department.
BG&E officials encourage customers to call at the slightest hint of the rotten egg odor that comes from a chemical mixed with natural gas -- which is odorless -- to provide a distinctive scent.
When a gas leak is reported to BG&E through its hot line -- (301) 685-0123 -- a crew should arrive within 25 minutes. The service is free, and the number is printed on every BG&E bill, Mr. Griffin said.
The utility also sends a yearly reminder in its bills -- a scratch-and-sniff card that reminds customers of how gas smells.
BG&E receives 125 to 200 calls a day from customers reporting the smell of gas, he said. About a quarter are related to gas problems -- most commonly a small leak from an extinguished pilot light on a gas stove. The other 75 percent are prompted by odors other than gas, Mr. Griffin said.
Inside the home, gas leaks often result from stoves' being left on or from aging appliances, such as gas water heaters.
Leaks also may develop years after an indoor pipe is dented or nicked. The nicked spot will corrode faster than the rest of the pipe, Mr. Griffin said.
"People will hang wet wash on gas lines, and it'll actually pull down the lines," he said. "Or there are cases where contractors have dented the lines. They should report it, but a lot of times they don't."
A customer who calls the BG&E hot line will be told to ventilate the house by raising windows, but to avoid turning on any switches or lighting matches. If enough gas accumulates in the air to form a mixture that is 10 percent gas, the slightest spark can ignite it, Mr. Griffin said.
BG&E is responsible for main taining outdoor gas pipes, and workers check them periodically for leaks. Construction work is the most common cause of gas leaks in outdoor pipes, Mr. Griffin said.
Officials at the Public Service Commission, which monitors BG&E's adherence to federal and state laws, say the utility has little control over construction crews.
Construction companies are required to notify all utilities -- through a one-number service called Miss Utility -- two days before they begin digging to ensure that no utility lines are in jeopardy. But enforcement of the law is minimal, said Alex J. Dankanich, a utility safety engineer at PSC in Maryland.
He said anyone who hires a construction crew for any project that requires digging should ask whether the utilities have been notified. Notification allows the utilities to mark their lines on the construction site.
"Lots of times they won't break it [a gas pipe]. They'll nick it or dent it, and in five years it'll fail at that spot," Mr. Dankanich said.
In Pennsylvania, a contractor installing sewers dented pipes that later caused three explosions in one block.
If a gas pipe leaks, BG&E crews may detect the problem through spot surveys using an electronic monitor that can detect a leak from above ground. But a more likely scenario is that the gas, which is lighter than air, will travel underground and find a place to escape. In that case, BG&E relies on customers to report the smell of gas.
In an open area, gas will mix with enough air to remain harmless. If the gas accumulates in a closed area, such as an airtight house, BG&E officials say the odor is so strong that most people notice it before it reaches a 0.5 percent mixture with air.
"You have to know that if you smell this odor in the air, you call somebody," Mr. Dankanich said.
Where to call
VTC If you smell gas, the Baltimore Gas and Electric Co. asks that you call its hot line: (301) 685-0123.
Construction companies that need information on underground utility lines, including gas pipes, should call (800) 257-7777.