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.
The coroner ruled Sidloski’s cause of death as drowning with a contributing cause of carbon monoxide intoxication. When her parents first found out she drowned, they said they were confused.
“Ally knew how to swim. It didn't make sense,” Tracie Sidloski, Ally’s mom, told TODAY.
“It doesn't feel real,” David Sidloski, Ally’s dad, added.
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The family spoke out about the incident for the first time, hoping to turn their tragedy into a life-saving warning.
The U.S. Coast Guard reported 41 incidents of boat-related carbon monoxide poisoning and five deaths in 2020.
Experts said carbon monoxide from a boat’s engine can build up, especially while the boat is idling or moving at slow speeds, creating an invisible cloud of toxic gas that can cause lethargy, headaches and nausea. Too much exposure can be lethal, so people should avoid breathing in the exhaust expelled from the engine, which is usually located in the back.
The Sidloski family attorney rented a boat similar to the one Ally was riding in for a demonstration. Friends who were with her on the vessel that day said she was sitting in the back, in an area known as the swimming deck. There are places shaped like seats, cushions and even a cup holder for drinks. But those are not designated seats, according to the boat maker.
The Yamaha owner’s manual states: “Passengers must always sit in a designated seating area.” A diagram highlights certain seats as safe, but not the swimming deck. Yamaha also warns: “Stay away from the swim platform area while the engines are running. Exhaust gases coming from underneath it contain carbon monoxide.”
But attorney John Uustal, who plans to file a lawsuit on behalf of Sidloski’s family, said “this is not a problem to be solved in the owner’s manual. There should not be seats in the danger zone.”
Yamaha declined to be interviewed. “We do not make comments regarding current, pending or possible litigation,” the company wrote in a statement.
Swimming decks can be particularly dangerous when the engine is on because the area is right on top of where it vents the exhaust, the Centers for Disease Control and Prevention, the U.S. Coast Guard and the National Marine Manufacturers Association said. It’s a tempting place to hang out because it’s comfortable, but people need to pay attention to where they sit and whether they’re starting to feel symptoms.
To understand how quickly carbon monoxide can build up in that area of the boat, TODAY used a carbon monoxide meter to measure the fumes. Any reading above 200 parts per million sets off an alarm. With the boat engine idling, it only took a few minutes for that to happen. The reading spiked to 700 parts per million at one point.
“That is definitely a danger zone and you should remove yourselves and your children from that area of the boat immediately,” said Dr. Bill Benda, an associate professor of emergency medicine at Florida Atlantic University who is also an avid boater.
He believes carbon monoxide poisoning incidents are under-reported because victims often don't tell doctors the circumstances around which they started feeling ill. “So we assume it's something much more simple and common like dehydration, sun exposure, alcohol use, seasickness,” Benda noted.
Experts also warned people shouldn’t swim near an idling boat. When TODAY took the carbon monoxide meter to a popular swimming spot in Florida and measured the air around various boats, the readings climbed to up to 400 parts per million.
Symptoms to watch for:
If anyone on the boat starts feeling sleepy, nauseated or dizzy, move to the front of the vessel to get fresh air. Keep a life vest on just in case. Kids are more sensitive to the fumes because of their smaller bodies so monitor their breathing and if it stops, perform CPR and call 911.
If you’re in the water and start feeling unwell, get out and return to solid ground. If the symptoms are severe, Benda advised going to the emergency room and telling doctors you suspect you may have carbon monoxide poisoning — they may treat you with oxygen.
Boat owners may consider buying a carbon monoxide meter, which costs less than $100 and is a good indicator of when the levels of the gas might be too high or which areas of the boat are more likely to have gas build-up.
The U.S. Coast Guard offers a carbon monoxide safety checklist that urges owners to check for exhaust leaks and inspect rubber exhaust hoses once a month, and to always let all passengers know about the symptoms of carbon monoxide poisoning.
Meanwhile, Ally Sidloski’s family hopes her legacy will save lives.
“We can't bring our daughter back. But if we can try to save other people from having to go through this, we want to do our best to do that,” her mom said. “It is preventable.”
This story first appeared on TODAY.com. More from TODAY: