HOBART | The carbon monoxide level in the Arc BRIDGES group home where a woman died Saturday was about 100 times higher than what is considered safe.

Hobart Assistant Fire Chief Steve Mast said some areas of the home reached 1,000 parts per million of carbon monoxide. In ideal conditions, a carbon monoxide level is zero, but up to nine parts per million is normally acceptable.

"Over nine is usually unsafe to occupy the building," Mast said. The Occupational Health and Safety Administration allows workers to be exposed to carbon monoxide at levels up to 35 parts per million during an eight-hour shift.

"Levels of 100 parts per million or greater are usually potentially lethal," Mast said.

Toby Sandilla, 55, died Saturday morning in the home at 420 Crestwood Drive. Six others, including two police officers, were taken to the hospital for treatment. City inspectors said a faulty flue on a water heater caused the leak.

Hobart police Lt. Leo Finnerty said the incident is being investigated, including whether carbon monoxide detectors in the home were working.

Mast said it was unclear how long the odorless, colorless gas had been leaking into the home. The only way to determine that, he said, would be to air out the home and restart the faulty water heater and see how long it took for the level to rise that high.

"It could be hours to days," he said.

Firefighters without a breathing apparatus had to do "snatch-and-grab" rescues for the residents in the home since the carbon monoxide levels were so high.

Before Saturday, Mast said the highest level of carbon monoxide he had ever seen was 400 parts per million, which occurred when a woman was cooking on a faulty stove.

Low levels of carbon monoxide can cause flu-like symptoms, including headaches, drowsiness and nausea. Saturday's levels were so high it was surprising there was only one fatality, he said.

"I'm very thankful that was all it was," Mast said.