DENVER -- Denver firefighters believe that carbon monoxide claimed the life of a 23-year-old woman at the Josephine Place Apartments near Denver University, and left another resident hospitalized.

The dead woman was identified Tuesday as Lauren Johnson, a University of Denver graduate student. The Vancouver, Wash., resident was in her first year of the human rights program at DU's Josef Korbel School of International Studies, said DU spokesman Jim Berscheidt.

Authorities said a woman who lived in the apartments in the 2100 block of Josephine Street, called 911 shortly before 5 p.m. Monday saying she felt woozy.

Firefighters discovered the woman groggy when she answered the door. Another woman in a nearby third-floor apartment, believed to be Johnson, was found unconscious.

Johnson was rushed to Porter Adventist Hospital, where she was pronounced dead.

Firefighters found extremely high levels of carbon monoxide in the building.

"That unit tested out at about 1,500 parts per million," said Denver Fire spokesman Lt. Phil Champagne. "The normal threshold is about 35 parts per million."

Carbon monoxide in concentrations of 1,200 parts per million can be fatal, Champagne said.

The Denver coroner conducted Johnson's autopsy on Tuesday, but the results are not expected for several days.

Firefighters initially said a gas-fired boiler system in the building probably malfunctioned, but on Tuesday, investigators began looking at the boiler vent. Firefighters say the flue was damaged and not properly attached, causing carbon monoxide to build up.

The flue from the boiler had been repaired Monday after wind damage last week, Champagne said. He said the venting system was working properly until it was repaired, when the person who repaired it just used the old cap and did not properly attach it.

Champagne said authorities will review whether the person who replaced the cap was negligent. Fault could fall on the owners of the apartment complex or on the repair crews, Champagne said.

The improperly installed flue is located next to Johnson's unit -- 312. The other victim lives nearby, in Unit 314.

The second victim, who remains hospitalized, has not been identified. Authorities have not released her condition but said her injuries are not considered life-threatening.

Residents of the 42-unit complex were evacuated for hours after firefighters found high levels of carbon monoxide.

Champagne said he believes had the complex not been an open-air building, the number of casualties could have been catastrophic.

Johnson Remembered By Family, Friends

Johnson's friends say she will be missed. A family friend said Johnson was a remarkable and gifted young lady.

Her parents live in Windsor and were very supportive of her work in international studies.

Firefighters Emphasize Importance Of Carbon Monoxide Detectors

Stunned neighbors said the incident is a wake-up call and a grim reminder that a $30 investment in a carbon monoxide detector can save lives.

"I think it's a good idea to have one, just in case. I mean you'd rather have one and never have it go off than not have one and have something bad happen," said Jenny Saulson, who lives in the complex.

"It's pretty important now, especially with what happened," said resident Julio Perdomo.

Although many of the residents of the Josephine Place Apartment buildings are DU students, the complex is not owned by DU.

Johnson's death lends urgency to State Rep. John Soper's proposed carbon monoxide detector legislation. The bill would require carbon monoxide detectors in new homes, homes being put up for sale and apartment units being turned over to new tenants.

The city of Denver does not require carbon monoxide detectors installed in the building or in the apartment units.

Doctors at Presbyterian St. Luke's said carbon monoxide poisoning is not uncommon. The hospital treats 50 patients a year in its submarine-like hyperbaric chamber.