Too Often, This Silent Poisoning Happens On Board

It is not the pandemic, seasickness, flu, or your lunch.  Carbon Monoxide is dangerous.  Victims need to find fresh air immediately.  This happens on boats more than you think.

By Tom Beardsley, Finger Lakes Chapter

(This story was originally published in the March 2021 issue of Brightwork. Within the story is a report of an unidentified youth who succumbed to CO exposure while on an open boat several years ago on a lake in Oklahoma.  Due to lobbying efforts by his mother, Cassie Free, a new state law has been passed requiring a placard to be installed on boats advising the dangers and symptoms of such exposure.   Called “Andy’s Law” in honor of her son, Andy Free, the law unanimously passed through the Oklahoma house, is moving to the state senate and is expected to pass. More information can be found here from a Tulsa news outlet:” “Andy’s Law” is a timely update for the re-publication of this article.)


Odorless, shapeless, and colorless, this binds to the hemoglobin in your bloodstream, diminishing the oxygen carrying capabilities.  A victim might notice a dull headache which becomes severe pretty quickly.  Nausea comes next and vomiting can be violent.  Confusion is likely and with nothing obvious to explain the symptoms there may be a reluctance to call for help.  Chest pain, shortness of breath and loss of consciousness will follow without intervention.  This is a deadly poisoning by carbon monoxide, known after the fact as COHb (carboxyhemoglobin).

Severe winter weather in places like Texas recently have made this tragic story too common. 

We usually read of carbon monoxide (CO) poisoning due to faulty garage heaters, water heater vents, stoves and furnaces, but it happens on boats far more often than you may think and not only from the shop heater during winter work.  Bad exhaust systems and engines out of tune can be a problem.  Sometimes, even a good exhaust can backdraft into the cockpit while cruising on a warm, summer day.  CO can simply surround a boat at anchor or at the dock.

It is important to know the symptoms which can present and the damage which can be caused.

How can it happen on a boat?

Summertime boat incidents of CO poisoning are sometimes difficult to recognize in early stages.  Symptoms are often confused with seasickness, too much sun, too much to drink or too much to eat.  While hundreds of headlines appear with stories of people overcome by carbon monoxide in garages, too seldom are we reminded of the same thing which happens outdoors in nice, warm weather.

There are many cases, according to safety bulletins from the U.S. Coast Guard of COHb occurring when boats are moored against each other and swinging at anchor while people enjoy a summer day, swimming, eating or drinking.   One of the boats may have a generator or other engine running and soon, a number of people are overcome. 

Even open boats are susceptible.  Sunbathers on the swim platform or the back bench have been victims, even if underway. 

It Works Like This:

Oxygen binds to hemoglobin and is circulated through the body.  CO displaces that oxygen, binds to the hemoglobin and is unable to transport any oxygen at all.  The result is cellular damage which, if caught early, can be temporary.  A lengthy exposure among survivors might require therapy.

Exhaust from near by vessels can send CO into your boat’s cabin or cockpit.

According to Dr. Eric Walter, a pulmonologist and critical care doctor with the Kaiser-Permanente Sunnyside Medical Center in Portland, Oregon, CO poisoning accounts for about 50,000 emergency room visits in the United States each year.  It is considered one of the leading causes of poisoning deaths although only about 3% of such poisonings are fatal.  Dr. Walter, in an article published in Critical Care Alert, says that a hyperbaric chamber is the preferred treatment.

Upstate Medical Center in Syracuse has such a facility and it is the only 24/7/365 Hyperbaric treatment center in central and western New York.

Hyperbaric chambers are generally associated with “The Bends,” a condition rendered in SCUBA diving when excess nitrogen is trapped in the bloodstream.  This most often happens with too fast an ascent after an extended stay underwater.  Despite that, hyperbaric chambers are actually used more often in CO cases with a “goal to decrease short and long-term neurocognitive dysfunction,” says Dr. Walter.

Whether it happens in the winter or the summer, the symptoms of CO poisoning are the same and they are not pleasant.

Back drafting can occur when a boat is operated at a high bow angle.

A nationally registered paramedic, Barry Nickelsberg, responded to a call in the winter while working in Illinois.  The call came in as “male with severe vomiting.”  Nickelsberg says when they arrived, the entire family of five was stricken. Suspecting CO poisoning immediately, the crew got everyone outside right away.  They transported the entire family to the hospital.   

“The pulse oximeter we had wouldn’t tell us anything.  The way CO binds in the bloodstream, mimicking oxygen (O2), the oximeter would simply show 100% perfusion or saturation.  We needed to get these people to the hospital for a blood test which could measure their COHb.  The youngest, a girl about 5 years old, presented with very red cheeks, everyone else looked normal, except for being sick.”

Dr. Walters says victims often look “normal.”  The “Cherry Red” complexion which people think is typical is actually close to end stage.  “It’s rarely seen,” Walters writes.  “When the red complexion is seen, the COHb levels are usually at lethal stages.”

The CDC (Centers for Disease Control),  says symptoms of COHb can progress fairly quickly, depending on ventilation and the size of the area.  A victim might first notice flushing of the cheeks followed by or concurrent with a headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion.  Unconsciousness may come on quickly, followed often by death.

The days when the back window of the station wagon opened sometimes drafted carbon monoxide into the car. The cockpit of a boat, particularly with a windshield and biminy, has had this happen, too.  Exhaust can be drawn into the area from the back of the boat – even while moving.

In June, 2020, a family was tubing  on an Oklahoma lake.  A nine year old boy was getting cranky and seemed tired, according to his mother.  Back at the dock, he fell off the boat, unconscious.  In spite of rescuers’ attempts, the boy did not survive.

In an interview with national press, the mother said her son had a carboxyhemo– globin level of 72, meaning 72% of his blood was incapable of carrying oxygen. She held interviews with the hope of bringing awareness to others, saying this was a normal, sunny, warm day on the water.

In Fulton, NY back in the 1980’s, a couple was killed on board a boat when a generator’s exhaust caused a build-up of CO gases.  

In Long Beach, CA the owner of a cabin cruiser he was restoring was killed from the exhaust of a portable generator in 2016. 

In Rome, NY early in the summer of 2020, two people were killed, one of them was an off-duty Syracuse police officer from CO. 

In the case of the Fulton incident, first responders who administered CPR (back in the days of mouth-to-mouth rescue breathing) suffered long-term joint pain, another symptom of this poisoning

Often, even if an unconscious victim is rescued, the injuries may be debilitating to the point that recovery may not be possible.  Doctors also say that infants, elderly and others with chronic heart disease, breathing issues, pulmonary illnesses or anemia may be most at risk for long-term damage.

How to Detect and Stay Safe:

Credit: Aircraft Owners & Pilot’s Assn.

At home, code says at least one CO detector should be installed.  A single household can have a plug-in unit, multiple or commercial dwellings should have a hard-wired unit.  Combination smoke and CO detectors are available.

The smart pilot of an airplane will have a CO monitor in the cockpit.  A smart boater will have a marine grade unit installed onboard.  

Devices can be installed on the console of a boat and in cabin spaces.  They range from electronic devices with alarms to simple dots which change color when CO is detected (units in sleeping spaces should always have an audible alarm).

Batteries (if equipped) should be replaced at the beginning of each season and the unit should be replaced according to manufacturer’s recommendations (writing the installation date on the unit with a marker may help).

The Coast Guard publication on carbon monoxide safety states:  “Install and maintain a working CO detector listed by Underwriters’ Laboratories (UL) as appropriate for marine use inside the boat.”   The publication adds:

  • Properly install and maintain all fuel-burning engines and appliances.
  • Educate all passengers about the signs and symptoms of CO poisoning.
  • Swim and play away from areas where engines vent their exhaust.
  • Watch children closely when they play on rear swim decks or water platforms.
  • Never block exhaust outlets. Blocking outlets can cause CO to build up in the cabin and cockpit areas–even when hatches, windows, portholes, and doors are closed.
  • Dock, beach, or anchor at least 20 feet away from the nearest boat that is running a generator or engine. Exhaust from a nearby vessel can send CO into the cabin and cockpit of a boat.

Because carbon monoxide binds to hemoglobin so strongly, you can be poisoned by carbon monoxide even at very low concentrations if you are exposed for a long period of time. Concentrations as low as 20 or 30 parts per million (PPM) can be harmful if you are exposed for several hours. Exposure at 2,000 PPM for one hour will cause unconsciousness.

If you think a person on your boat has CO poisoning move him or her to fresh air right away and contact the nearest emergency services.


Carbon Monoxide Fact Sheet

.5 to 5 ppm      Normal Level in Home

5 to 15 ppm     Acceptable Level Near Furnace

35 ppm            Workplace limit—8 hour average

100 ppm          Leave Area Immediately

200 ppm          Dizziness, Nausea, Fatigue

400 ppm          3 Hour Exposure May Be Fatal

800 ppm          2 Hour Exposure May Be Fatal

6,400 ppm       30 Min Exposure = Unconsciousness/Death

12,800 ppm     1 to 3 Min Exposure = Unconsciousness/Death


Researching this story found hundreds of recent CO poisonings.  Each anecdote we found had one of two story lines:  1) The good Samaritan or medic discovered the event – and figured it out – just in time to save the victims, sometimes with hospitalization or  2) Tragic loss of life.

Brightwork urges its readers to include checking the exhaust system at the beginning of each season.  Make sure there are no leaks by putting soapy water on the (cold) exhaust line and start the engine.  Look for bubbles and look for water leaks from a wet exhaust.   Check the exhaust port on the outside of the boat.  It is not just for show and should not be rusty, pitted, bent or broken. Don’t run the boat in an enclosed or even partially enclosed boat house, particularly not to “warm it up” or for maintenance.  Ventilate your shop area when working with paints or indoor shop heaters.  Leave your generator outside and aim the exhaust away from the building, doorways, windows and air vents.

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