Last week's carbon monoxide leak in a South Anchorage home, which killed a teenager and sickened seven family members, has been traced to a detached exhaust pipe on a heating system boiler in the garage.
Anchorage Police Department Lt. John McKinnon said Monday that it wasn't clear how the pipe became separated from the natural gas-fired boiler, one of two in the garage at the Shoshoni Avenue residence.
"They sit side by side and one of them, the exhaust pipe that would send this stuff outside had been disconnected somehow," McKinnon said. "It was almost as if the pipe had been popped off and was disconnected."
Trevor Noble, 18, died at the home in the Feb. 20 incident. Medics took the rest of his family to hospitals for treatment of poisoning by carbon monoxide, an odorless, colorless gas that can cause disorientation, unconsciousness and death.
The Noble family declined to comment on the incident Monday.
Firefighters who entered the home reported levels of CO exceeding 1,000 parts per million, near the level at which it poses an immediate risk to human health, experts say.
The boiler had been serviced by a plumbing and heating firm within the past six weeks, said McKinnon, who oversees the police department's robbery/assault and homicide units, which have been investigating the incident. Police haven't found any sign that the exhaust pipe – a 4-inch line extending less than a yard from the boiler to an exterior wall – had been deliberately unhooked.
"It is possible that something may have caused the thing to pop off, like an air-pressure change; it's possible that it happened by accident," McKinnon said. "That thing's not protected by anything in the garage there, so it's possible that someone might have pushed it walking by it."
Once the exhaust hose became disconnected, however, it allowed the lighter-than-air gas to vent inside the home rather than outdoors. McKinnon said police didn't find any functioning CO detectors inside the home. It wasn't clear how long it would have taken carbon monoxide concentrations to reach lethal levels.
"The boiler sits right below the room where (Trevor Noble) sleeps," McKinnon said. "With it being such a big home, it's hard to say how long it might have taken to fill that home up long enough to cause symptoms, let alone death."
After consulting with Anchorage District Attorney Clint Campion's office, McKinnon said, police had closed their initial investigation with no charges filed. Civil actions filed in Noble's death by the family or others remained a possibility, however.
"Right now, we're looking at it as a tragedy," McKinnon said.