By Vicky Nguyen, Joe Enoch and Merritt Enright

Every year, thousands of people seek emergency care for poisoning from carbon monoxide — an odorless, colorless gas produced when fuel is burned. It can be deadly for humans and animals who breathe in the fumes.

Most people think of carbon monoxide as building up indoors, but it can also be a lethal danger out on the open water — one of the top five causes of boating-related deaths each year, according to the U.S. Coast Guard.

Ally Sidloski was 21 when she died in May. As a student and soccer player at the University of Cincinnati, she was the picture of health, her family said. But after a day of boating on an Ohio lake, she went into the water for a dip and never resurfaced.

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