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A Hidden Hazard

A Hidden Hazard

A Hidden Hazard


Workplace Safety Division
Directorate of Assessments and Prevention
U.S. Army Combat Readiness Center
Fort Rucker, Alabama


When considering the leading causes of boating fatalities, most picture lack of operator training, operating a vessel under the influence of alcohol or drugs, or falling overboard. While that is certainly true, there’s a lesser-known danger that can be equally as deadly when boating — carbon monoxide (CO) poisoning.

With summer just around the corner, many of us are already making plans to get our boats back on the water. Whether it is waterskiing, tubing, fishing or just cruising the lake, ocean or bay, few outdoor activities rival boating. But in addition to operator training and ensuring everyone onboard has a properly fitted U.S. Coast Guard-approved personal flotation device, we must all be vigilant about the dangers of CO poisoning, which ranks fifth in the top known causes of death among boaters.

Carbon monoxide is a toxic, odorless, colorless, tasteless gas produced by the burning of carbon-based fuels. When breathed in, it displaces oxygen, depriving the vital organs. On boats, CO is emitted by engines, gas generators, cooking ranges and heaters. The build-up of CO inside boat cabins, partially enclosed cockpits, beneath swim platforms or other enclosed areas is potentially deadly. In high concentrations, CO can be fatal in a matter of minutes. What’s worse is CO poisoning and seasickness often share the same symptoms, including drowsiness, nausea, fatigue and loss of judgment, which can make it difficult to detect.

These days, most boats are equipped with CO detectors that can help identify potential exposure. However, these detectors can be susceptible to false alarms. Battery powered detectors are also at risk of going dead if not checked frequently, which renders the device useless. If the CO detector sounds an alarm and the engines or generators aren’t running, it might possibly be sensing toxic gas from the boat next to you. Either way, consider testing or replacing the CO detector in accordance with the manufacturer’s recommendations or as part of an annual safety check.

It is common for operators to keep their engines or generators running to power air conditioners, galley appliances and the suite of electronics in these new, tech-savvy vessels. When the generator is running, the CO gas can buildup in the cabin, on or near the swim platform, and close to the rear deck space. This poses an imminent danger of death for anyone in or near these areas — even for a very short period of time. For that reason, all owners and operators of vessels equipped with swim platforms and gasoline-powered generators with exhaust ports on the transom are advised to turn off their generators when their boats are anchored or moored and passengers are on or near the swim platform or swimmers are in the water. Keep passengers, particularly unsupervised children, off the back deck or a swim platform while gasoline engine(s) or a generator are running.

Other CO sources include flame-producing devices in an unventilated area such as heaters, stoves and lanterns. Alcohol heaters and stoves, propane heaters and stoves, catalytic heaters, oil lamps, gasoline lanterns, and charcoal stoves consume oxygen. Ventilation must be provided whenever any device producing an open flame is used in a boat cabin.

To help prevent a CO exposure, the U.S. Coast Guard recommends boaters:

  • Educate all passengers about where exhaust outlets are located on the vessel, the symptoms of CO poisoning and where CO may accumulate.
  • When docked or rafted with another boat, be aware of exhaust emissions from the neighboring vessel.
  • Listen to any changes in exhaust sound, which could indicate an exhaust component failure.
  • Check the operation of each CO alarm by pressing the test button.

At least monthly you should:

  • Make sure all exhaust system clamps are in place and secure.
  • Look for potential sources of leakage from exhaust system components. Signs include rust and/or black streaking, water leaks, or corroded or cracked fittings.
  • Inspect rubber exhaust hoses for burned, cracked or deteriorated sections. All rubber hoses should be pliable and free of kinks.
  • Inspect and confirm that there are no leaks around the cylinder head gaskets, exhaust manifold gaskets, water injected exhaust elbows, pipe nipples between water injected elbows and exhaust manifolds, and exhaust pipes, hoses and fittings.

At least yearly you should have a qualified marine technician:

  • Replace exhaust hoses if cracking, charring or deterioration is found.
  • Ensure your engines and generators are properly tuned and well-maintained.
  • Inspect each water pump impeller and the water pump housing. Replace if worn. Make sure cooling systems are in working condition.
  • Inspect all metallic exhaust components for cracking, rusting, leaking or loosening. Make sure the technician checks the cylinder head, exhaust manifold, water injection elbow, and the threaded adapter nipple between the manifold and the elbow.
  • Clean, inspect and confirm proper operation of the generator cooling water anti-siphon valve (if equipped).

For more information about boating safety, visit the Centers for Disease Control and Prevention’s website at https://www.cdc.gov/co/boating.htm or the U.S. Coast Guard’s website at https://www.uscgboating.org.



No Teak Surfing!

Teak surfing, also known as platform dragging, drag surfing and teak boarding, is when an individual holds onto a boat’s swim platform or ladder and attempts to body surf the vessel’s wake. The U.S. Coast Guard warns this dangerous practice puts the “surfer” directly in the path of the vessel’s exhaust and exposes them to dangerous levels of carbon monoxide. In addition to carbon monoxide, teak surfers are exposed to a boat's propeller. A typical recreational propeller can travel from head to toe on an average person in less than one-tenth of a second. Following the deaths of several teak surfers, some states banned the dangerous practice. Boat operators can also be fined for allowing passengers to teak surf on their vessels.



  • 6 June 2021
  • Author: USACRC Editor
  • Number of views: 851
  • Comments: 0