Most of us have been too close to the rail when backing down or when the right gust of wind pushed 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 choke when the air is otherwise calm. Fuel exhaust smells and tastes bad and avoiding it is almost automatic. The problem is, the part that smell bad and tastes awful isn’t the part that is immediately dangerous.
Carbon Monoxide (CO) smells like nothing and tastes like nothing, and while it is always present in the smelly exhaust, it can build up and creep into the air you breathe without giving you any warning. Just a few breaths in concentration can make you sick, or worse, you can go to sleep in your boat thinking everything is fine, and simply not wake up.
This is another one of those areas where regulations require inspections for commercial vessels, but that used cabin cruiser you just bought may be leaking CO from a half dozen hose connections. And even on the open deck of a new vessel, under the right conditions, breathing exhaust fumes can cause fast injury to you or your passengers. Besides regular (at least annual) inspections by a certified marine mechanic, boaters should know the signs of CO poisoning and the ways it can be prevented.
Signs and Symptoms
When a person inhales carbon monoxide, in any amount, just like oxygen molecules, the gas passes into the bloodstream through the lungs and attaches itself to red blood cells. It is actually better at this attachment than oxygen is.
Besides displaces the oxygen around it, once it binds to a red blood cell, that blood cell is unavailable to an oxygen molecule, and you need those – really. 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 of those.
When someone feels seasick who doesn’t usually get seasick, the cause may be CO. Other signs besides nausea include, headache, confusion, fatigue, dizziness, or even seizures.
What to Do
If you notice these symptoms in yourself or others, step one is to get them to the freshest air available 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 just seasickness, particularly if there is obvious exhaust present on deck (or below).
The CO bound the blood cells 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 or CO. Shutting the engines down or heading into the wind can help ensure clean air to breath. Pure oxygen is best to breath during recovery, but few of us have that in our medical kits, but that is what first responders will administer when they arrive.
If the poisoning is bad enough, hospital treatment may involve spending time in an oxygen pressurized oxygen chamber. Again, that CO is really good at attaching itself to red blood cells and the pressure gives the O2 and advantage.
Avoid the CO is a Better Plan
The first and best thing you can do to avoid CO build up on your vessel is regular exhaust system inspections and maintenance. Lack of maintenance is almost always the cause of CO build up inside vessel spaces, so regularly inspect exhaust hoses, and hose connections for leaks, charing, looseness or any deterioration and replace them if you find problems.
But even on well-maintained vessels, CO build up in the cabin spaces can occur while at idle or when operating at speed with a high bow angle. Back drafting can occur or the CO can find its way in through other hull openings.
After one incident along the Gulf Coast last year, the U.S. Coast Guard released Marine Safety Alert 10-17 that describes how the design of the swim platform and transom created a condition where an otherwise perfectly maintained vessel would build up high concentrations of CO on the back deck, fly bridge, and even into the cabin spaces. One one trip, multiple passengers had to be hospitalized.
The USCG has some excellent guidance on ways to prevent and avoid CO problems on your vessel. Take a moment to read through them (linked her) and make sure you are paying attention to this danger that you can’t actually see.