21-people were sickened by carbon monoxide on a house boat on Lake Powell in Arizona.
The National Park Service was called received a call around 12:45 a.m. on Tuesday about the possible poisoning incident on a private boat in Face Canyon in the Glen Canyon National Recreation area.
Park rangers responded immediately and provided medical support on scene. Personnel from Classic Air Medical dispatched 3 medical helicopters and Intermountain Life Flight dispatched 2 medical helicopters.
Three adults and two children were flown to the St. George Regional Hospital in Utah for treatment. The remaining 16 patients were treated and released at the scene.
The source of the carbon monoxide was unknown but was under investigation.
This is the third carbon monoxide-related incident responded to by Glen Canyon National Recreation Area Rangers this month.
The park service warned boaters that should be aware of the dangers of carbon monoxide (CO) and ensure on-board CO detectors are operable.
Carbon Monoxide is an odorless, tasteless gas that can cause death when inhaled.
Symptoms of exposure can include headaches, dizziness, nausea, vomiting, and confusion. A person who is sleeping can die from CO poisoning before recognizing symptoms.
Boats can collect dangerous levels of CO anytime fuel-burning, engines or appliances are running.
