Lake Powell, AZ – An Arizona man died Tuesday in the Glen Canyon National Recreation Area as he tried to evacuate family from a rental houseboat filled with carbon monoxide.

Brent McGinn, a chief ranger with the National Park Service, said this afternoon the carbon monoxide was produced by a generator providing electrictiy for the houseboat. There were working carbon monoxide detectors on the boat, McGinn said, but investigators are unsure whether the occupants had the windows of the boat open.

Glenn Howeth, 62, suffered a heart attack while trying to wake family members after he found his grandson passed out on the floor of a houseboat, the park service said. Howeth realized carbon monoxide poisoning was likely to blame for his grandson’s condition and started alerting other family members around 3 a.m. to escape to the boat’s outside deck, said McGinn.

Another one of Howeth’s grandsons performed CPR on him after the heart attack. Emergency personnel later arrived and could not revive him.

Seven of Howeth’s family members aboard the 75-foot Aramark rental houseboat were flown by helicopter to a hospital in Page, Ariz., for treatment for carbon monoxide poisoning, McGinn said.

Six people were then transferred to Dixie Regional Medical Center in St. George for treatment in a hyperbaric chamber.

Two people showed signs of “decreased mental ability” and must undergo additional tests before they can be released from the hospital, McGinn said.

Rangers are inspecting the houseboat, which was moored in Rock Creek Bay.

McGinn said Aramark owns 25 rental houseboats on the lake.

Carbon monoxide is an odorless, colorless gas that can build up in lower levels of boats with poor air circulation.

The Glen Canyon incident is the second incident in Utah this week where people were hospitalized after carbon monoxide exposure.

Six people in Ogden survived a carbon monoxide scare early Tuesday.

The Ogden City Fire Department responded to 1003 E. 125 South around 2:15 a.m. after someone called 911 to complain everyone in the house was fainting, said Deputy Chief Chad Tucker, a Fire Department spokesman.

A dispatcher told the caller to have everyone evacuate the house. Emergency personnel arrived to find six people outside the home; all complained of flu symptoms, Tucker said.

Firefighters discovered lethal amounts of carbon monoxide in the home. The six occupants of the house were taken to a local hospital.