STILLWATER, Minn. - News of another boating death from carbon monoxide poisoning was hard for John Tetzlaff, owner of Tetzlaff Yacht Sales, to hear.

"When I sell a boat, that's what I tell people – not to run their generator at night," he said.

The State Legislature just passed "Sophia's Law," named for 7-year-old Sophia Baechler, who died from carbon monoxide poisoning. It requires all boats with a cabin to have a carbon monoxide detector.

Tetzlaff wants to warn others about the importance of those detectors.

"The wind behind the boat can generate a backdraft, that could then flow carbon monoxide from the engines into the boat," Tetzlaff said. "And if that were the case, this would go off."

But Sophia's Law doesn't go into effect until May 2018. And over the weekend, authorities found three people unconscious inside their boat. One died and one is in critical condition.

"It was cold, they probably had the heater on," Tetzlaff said. "And they may have gone to sleep and not thought about it."

Tetzlaff says besides being aware of possible engine fumes drafting back into the boat, boaters need to remember carbon monoxide also comes from the generator, which boaters often use when anchoring.

Tetzlaff warns people not to run the generator at night if sleeping in the boat.

"Again, the exhaust is coming out the back, but easily could work its way back in," he said.

And lastly, Tetzlaff says it's important to act fast if carbon monoxide exposure is suspected.

"If you're driving and the carbon monoxide goes off, get everybody out of the cabin, into the cockpit area, open all the hatches and the canvas, and get air flow into the boat," he said.

The St. Croix County Wisconsin Sheriff's Department is still investigating the incident that happened over the weekend. They say they don't know if the carbon monoxide detector inside was working.