Four people were hospitalized yesterday after being exposed to carbon monoxide in their Hyde Park home, about 12 hours after firefighters tested the residence for the toxic gas and found no trace of it inside.
Steve MacDonald, a spokesman for the Boston Fire Department, said firefighters first responded to 71 Warren Ave. at 6:52 p.m. Sunday when the family reported their carbon monoxide detector had gone off.
“We did not get any readings inside the house on our meter and firefighters advised the homeowner to replace the battery,’’ MacDonald said. “The gas could have dissipated by the time we got there or there could be a problem with the detector.’’
He said that the meter used during the inspection has been taken out of service and that a private contractor would check to see whether it is working properly.
Firefighters returned to the home yesterday at about 7:30 a.m. after receiving a report of an unconscious person, and this time they found high levels of carbon monoxide with a second meter, MacDonald said.
All four occupants were able to walk out of the house and they were taken to Massachusetts General Hospital, according to MacDonald.
Jean Louisia, 61, speaking yesterday afternoon at his home, identified the occupants who suffered exposure as his wife, Evelyne, 54, and three of his children, Herline, 20, James, 17, and Carl, 15. He said everyone was expected to leave the hospital last night.
“Thank God,’’ Louisia said. “I feel lucky.’’
His wife and daughter were released last night, according to a hospital spokeswoman, but the conditions of his sons were unavailable because their names were not in the patient directory.
Louisia said that according to his family, Carl was temporarily unconscious in the home during the exposure.
Louisia said he was driving to work yesterday morning when he received a call from his daughter, who told him that everyone felt ill.
He said he was shaken by the news and told his daughter to call for an ambulance.
“I know about carbon monoxide, [I thought] that’s going to be big trouble,’’ Louisia said, adding that he does not blame the Fire Department for leaving Sunday night.
“I figured that it was my fault’’ because the windows were open when firefighters took the first reading, which may have caused the carbon monoxide to dissipate, Louisia said. “I can’t blame them.’’
He said he later closed all of the windows, and the detector went off again at about 12:30 a.m., prompting him to unplug it. MacDonald said that opening windows can lead to negative readings.
He said people should call 911 when detectors go off, but they should also keep their windows shut and wait outside for firefighters, so they can get an accurate reading when they arrive.
Louisia said inspectors told him that the exposure probably came from the water heating system.
He said that a plumber is scheduled to examine the system today, and that all of the heat was turned off in the house last night.
Louisia said his family was planning to stay with friends and relatives in Hyde Park and Randolph last night.
Mike Bello of the Globe staff contributed to this report. Travis Andersen can be reached at email@example.com. Follow him on Twitter @TAGlobe. Colin A. Young can be reached at firstname.lastname@example.org.