A persistent odor of gasoline in the Washington Hill neighborhood poses no health or fire hazards and should be cleared up in about a month, state rail officials said.
The aroma -- which some say is causing headaches and sore throats -- is emanating from a tunneling project for the Metro extension to Johns Hopkins Hospital.
"What we've learned here is that the human nose is as sensitive as any equipment we use," said Peter J. Schmidt, an assistant general manager for the Mass Transit Administration. "This has been a troublesome smell for people, but we can assure them that there are no dangers."
About 20 to 25 homes around East Baltimore Street and Broadway have had lingering gasoline odors throughout the buildings, because of vapors released during the underground digging two blocks away.
Rail officials were forced to stop tunneling to review the concerns of residents. "I would like to know what effect this gas will have on me, and I'd like this situation to be resolved," said Leslie Brinkley, 39, who lives in the 1700 block of East Baltimore Street.
Mr. Brinkley and about 40 other Washington Hill residents were told by rail officials Tuesday that monitored levels of gasoline in .. the affected homes show only minute traces of gasoline -- specifically, about 10 to 20 parts per million.
An MTA consultant physician said those levels have no long-term health implications. In addition, gasoline is only explosive at 3,000 to 4,000 parts per million, rail officials said.
All of the people with complaints have been visited by MTA officials and have been instructed on how to ventilate their homes to get rid of the smell.
MTA will compensate those residents whose heating bills increase because of the added ventilation, Mr. Schmidt said. A plastic waterproof liner is being installed in the rail tunnels and should make them airtight in about a month, Mr. Schmidt said.
Kenneth D. Merrill, the construction manager of the $321 million, 1.5-mile subway extension from Charles Center, said the gasoline vapors have been trapped for about 15 years. A now-defunct gas station at Broadway and Orleans streets likely leaked gas underground, and it remained there until the rail project disturbed it, Mr. Merrill said.