Carbon monoxide (CO) is a colorless and odorless gas that can poison or kill someone who breathes too much of it.
Some boats have engines that vent toward the rear of the boat, creating the potential for CO poisoning to kill people near the stern, on the rear swim deck, or in the water behind the boat. This danger is much greater in certain boat designs.
Boat manufacturers and sellers do not give enough warning about this danger, and most boaters don’t realize the danger zones on a boat or the safety risks faced.
CO that builds up in the air space beneath the stern deck or on and near the swim deck can kill someone in seconds.
Carbon monoxide is a component of exhaust gases – if you can smell exhaust then CO is present. Carbon monoxide is also produced when propane, charcoal, or oil burns to power onboard appliances such as a stove, grill, hot water heater or generator. The most common source is the gasoline-powered engine which is found on the majority of recreational motor boats. For this reason, it is important to know the sources of CO, the symptoms of CO exposure, and what to do if you suspect someone has been exposed to this deadly gas for any period of time.
To avoid CO you should know the areas of where CO can accumulate such as inadequately ventilated canvas enclosures and engine compartments. If you are tied to a dock be certain exhaust ports aren’t blocked which can force exhaust back into the boat and if you are rafted to another boat be certain exhaust from one boat doesn’t enter the other. Another way for exhaust to enter a boat is when a moving boat creates the station wagon effect where exhaust finds its way back aboard because of circular airflow known as back drafting.
How CO Can Build Up In a Boat
Larger boats, such as houseboats, sometimes have generators that vent toward the rear of the boat. This venting poses a danger of CO poisoning to people on the rear swim deck or water platform. On larger boats CO builds up above the water near the water platform. CO that builds up in the air space beneath the stern deck or on and near the swim deck can kill someone in seconds.
Traveling at slow speeds or idling in the water can cause CO to build up in a boat’s cabin, cockpit, bridge, and aft deck, or in an open area. Wind from the aft section of the boat can increase this buildup of CO.
Back drafting can cause CO to build up inside the cabin, cockpit, and bridge when a boat is operated at a high bow angle, is improperly or heavily loaded, or has an opening that draws in exhaust.
How to Prevent CO Poisoning on Boats
- Install and maintain a working CO detector listed by Underwriters’ Laboratories (UL) as appropriate for marine use inside the boat.
- 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.
Symptoms of CO Poisoning
The most common symptoms of CO poisoning are:
- Chest pain
High levels of carbon monoxide can kill you. Lower levels of CO can cause you to pass out and drown. And a person who is sleeping or intoxicated can die from CO poisoning before ever having symptoms.
If you think a person on your boat has CO poisoning move them to fresh air right away and contact the nearest emergency services.Sources: cdc.gov (Centers for Disease Control and Prevention) and boatus.org (Boat U.S. Foundation)