Monday 19th of October 2020

Carbon Monoxide Poisoning

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When I started my career as a marine surveyor, back in the early 1990’s, the firm that I worked for received several fatality investigations on rental houseboats. These were typically large fleets of houseboats built specifically for the rental industry. All of the incidents had a common theme; houseboat anchored or beached, engines secured, generator running, people (including the deceased) swimming.

The usual investigation involved travelling to the incident site (Lake Meade, Lake of the Ozarks, Shasta Lake, etc.), meeting with the local houseboat rental management, meeting with local law enforcement (usually park rangers), interviewing other members of the party, obtaining any produced reports and autopsies, and inspecting the vessel. Electrocution was usually suspected; but the cause usually was “undetermined”.

When I went out on my own in the late 1990’s I received an assignment to investigate a case involving a documented Carbon Monoxide incident on a private houseboat in Stockton, CA. Most of the passengers, and several law enforcement responders, had been taken to the hospital and diagnosed with CO poisoning. The local Sheriffs department had been investigating, and were concentrating on CO gas entering the vessel through the stern anchor hawse pipe, which ran through the engine room. However, there was no obvious way for the gas to go from the engine room into the rest of the vessel, where the passengers were located.

After inspecting the vessel, and speaking to the owner, I found out that again the engines were secured, the boat was beached onto the bank, and the generator was running. What jumped out at me was the routing of boat’s service items; all through the transom, along with the generator exhaust. That set up is pretty common. What was unusual was a solid welded aluminum swim platform, and sponsons that extended past the transom to the end of the platform, boxing in the transom on the top and the sides. Any exhaust gas exiting out the transom had about a 6” gap between the top of the solid swim platform and the sponson sides, to escape to atmosphere.

I then reviewed what I knew. I went back and spoke to the vessel owner and asked what the state of the tide was when the boat was beached. He said that when the tide went down, the bow stayed high on the beach and the stern was put partially underwater. Bingo. When the stern was put underwater there was no way for exhaust gasses to escape and they were pumped throughout the vessel through the gray water discharge piping and bilge pump discharges, creating essentially a floating gas chamber.

The lesson to learn here is to not overlook the obvious and simple explanations. If someone had connected the earlier unexplained houseboat fatalities with CO poisoning, lives may have been saved.