Do You Need a Carbon Monoxide Detector on Your Boat?

Short answer: if your boat has a cabin, a sleeping area or a generator, yes. Carbon monoxide (CO) is a colorless, odorless gas made whenever an engine, generator, heater or stove burns fuel. On a boat it can collect in cabins, under canvas and around the stern, often without anyone noticing until people feel sick.

Where CO builds up on a boat

• Cabins and sleeping areas: exhaust from your own engine or generator, or from a boat rafted alongside, can drift in through hatches and ports.
• The stern and swim platform: exhaust collects right where people board, swim and sit. Never let anyone swim near the stern or hold onto the swim platform while an engine or generator is running.
• Under canvas: bimini tops, side curtains and camper enclosures trap exhaust.
• Underway at slow speed: a high bow angle or a following wind can pull exhaust back into the cockpit (the "station wagon effect").
• Rafted up or docked next to boats running generators.

Warning signs

Early CO poisoning feels like seasickness or too much sun: headache, dizziness, nausea, tiredness and confusion. That's why it's easy to miss. If several people feel ill at once, or someone is unusually sleepy near the stern or in the cabin:

1. Get everyone into fresh air.
2. Shut off engines and generators.
3. Call for help (VHF channel 16 or 911) if anyone is confused, unconscious or doesn't improve quickly.

What the rules say

• Industry standard (ABYC A-24): the American Boat & Yacht Council standard covers marine CO detection. Many builders fit marine CO alarms in boats with enclosed accommodation spaces to meet ABYC standards.
• Minnesota's Sophia's Law: motorboats with an enclosed accommodation compartment (sleeping area, galley with sink, and toilet) must have a working marine CO detector meeting ABYC A-24, and gasoline motorboats with an enclosed occupancy space must display CO warning stickers at the helm, cabin entrance and stern. It applies to any boat on Minnesota waters. (MN DNR)
• Other states: rules vary and can change, so check with your state boating agency. Even where it isn't required, a CO alarm in any enclosed space is cheap protection.

How to choose a boat CO alarm

• Marine-listed: use a detector made and listed for boats (look for "marine" and ABYC A-24 on the product or manual). Household alarms aren't built for 12V systems, vibration and damp air.
• Power: 12V hardwired models such as the Safe-T-Alert 62 Series Marine run off the boat's battery; battery-powered models such as the Fireboy-Xintex CMD6 (internal battery) need no wiring, which suits smaller cabins and DIY installs.
• Relay output: some models can trigger a fan or shut down a generator when CO is detected.
• Propane aboard? If you have a propane stove or heater, look at CO + propane combo alarms in our CO & propane alarm collection.

Where to put it

• In the main cabin and within each sleeping area (Minnesota's rule: monitor the main cabin and each sleeping area, or within 10 feet of berths).
• Follow the maker's height and placement instructions, away from vents and direct engine-room openings.
• Hardwired units are best installed by a marine technician.

Keep it working

• Test it before each trip (it's on the pre-departure checklist in our Boater's Safety Pack).
• CO sensors wear out: most last about 5–7 years. Write the install date on the unit and replace it at end of life.
• Never ignore or disconnect an alarm because of "false alarms"; find the source.

Also have an RV?

Read our RV carbon monoxide & propane alarm guide.

This article is general safety information, not legal advice. Follow the alarm maker's instructions and your state's boating rules.