Many of us have been too close to the rail when backing our boats down or have had a gust of wind push exhaust fumes into our face. Spend any time fishing offshore and that time at idle while you pull in your catch can be enough to make you wheeze when the air is otherwise calm. Engine exhaust fumes smell and taste bad, so avoiding them is almost automatic. The problem is that the part that smells bad and tastes awful isn’t the immediately dangerous part. Carbon monoxide (CO) is. Odorless and colorless, while it is always present in smelly exhaust fumes, it can also stealthily build up and creep into the air you breathe without warning. Just a few breaths in high concentration can make you sick. Worse yet, you can go to sleep in your boat thinking everything is fine, and then simply not wake up.
That used cabin cruiser you just bought? It may be leaking CO from hose connections. But even if you have a newer vessel, its exhaust fumes may be harmful. For that reason, regular inspections by a certified marine mechanic are important. In addition, boaters should know the signs of CO poisoning and how to prevent it.
When a person inhales CO, no matter the concentration, the gas passes into the bloodstream through the lungs and attaches itself to red blood cells. It’s actually more readily absorbed into the bloodstream than oxygen. Besides displacing the oxygen around it, CO also renders your blood cells unable to absorb oxygen. Simply put, CO makes oxygen transfer impossible. So, the signs and symptoms of CO poisoning are a lot like those of altitude sickness. Nausea is just one. When someone feels seasick who doesn’t usually get seasick, the cause may be CO. Other signs include headache, confusion, fatigue,
dizziness or even seizures.
If you notice these symptoms in yourself or others, step one is to get to fresh air immediately and make at least a pan-pan call, if not a request for medical assistance. No, I’m not suggesting a distress call for obvious seasickness, but I am suggesting you at least consider that it may be more than seasickness, particularly if there are obvious exhaust gasses present.
The CO in the bloodstream will, eventually, let go and be expelled from the lungs the same way it came in, but only if the air coming into the lungs is free of CO. Pure oxygen is best to breathe during recovery, but few of us have that in our medical kits. Shutting the engines down or heading into the wind can help provide clean air to breathe. If the poisoning is bad enough, hospital treatment may be necessary.
The first and best thing you can do to avoid CO buildup on your vessel is regular exhaust system inspections and maintenance. Lack of maintenance is almost always the cause of CO inside vessel spaces, so regularly inspect exhaust hoses and hose clamps for leaks, cracking, charring, looseness or any visible deterioration.
Even on a well-maintained vessel, CO buildup in the cabin spaces can occur while at idle, or when operating at speed with a high bow angle. Back-drafting also can happen, and CO sometimes finds its way in through other hull openings.
After one incident along the Gulf Coast a few years ago, the Coast Guard released Marine Safety Alert 10-17, which describes how the design of the subject vessel’s swim platform and transom created a condition where an otherwise perfectly maintained vessel would build up high concentrations of CO on the back deck, flybridge and even in the cabin spaces. During one trip, multiple passengers had to be hospitalized.
So, besides keeping up with engine maintenance and being aware of the situations that cause CO to accumulate, how are you supposed to defend yourself against this odorless gas? Install a carbon monoxide detector. There should be one or more on every boat with enclosed living spaces. Most marine CO detectors wire right into your existing direct-current system and they all sound an alert when dangerous levels of CO are present. They’re easy for just about any boat owner to install, so there’s no excuse not to have one. Remember, the life you save could be your own.
This article originally appeared in the April 2020 issue.