Carbon Monoxide Poisoning
Carbon monoxide (CO) is an odorless, colorless gas produced as a by-product from the incomplete combustion of carbon-based fuels such as gasoline, diesel or wood. CO is absorbed in to the blood stream 200 times faster than oxygen (O2) and replaces the body’s oxygen with CO in the blood stream, which results in suffocating the victim. A mild exposure to CO can be reversed by moving the victim to an area free of CO with lots of circulating fresh air. On the other hand, serious, prolonged exposure to CO is a medical emergency that can lead to death.
All internal combustion engines emit CO, so do diesel engines to a lesser effect but the threat is still there. Diesel fuel has about 10% of the carbon content that gasoline has. In the early stages, the symptoms of CO poisoning are similar to seasickness and CO can kill in a matter of minutes. It is important to recognize the symptoms of CO poisoning which are headaches, drowsiness, and nausea.
This toxic gas can accumulate quickly, especially in confined spaces, and has deadly effects on those exposed to it. To avoid CO poisoning, be aware of the risk, ensure sufficient ventilation of exhaust gases, ensure that the exhaust systems of all diesel and gasoline engines are properly vented away from living and sleeping areas onboard vessels, properly install and maintain equipment, and use CO detectors
The Coast Guard reports that there were 51 injuries and 12 fatalities from accidental carbon monoxide poisoning on recreational boats in 2006 in the United States. Of these:
- 41 events happened in cabin motorboats
- 3 events happened in houseboats
- 6 events happened in open motorboats
- 1 event happened with a PWC
The lack of a carbon monoxide detectors
Significant carbon monoxide poisoning potential can be caused by any of the following:
- Teak Surfing
- Gasoline-powered engines operating while docked
- Rafted with other boats operating engines
- Swimming or floating near an idling boat engine
- Underway with improper cabin ventilation
- Swimming under or sitting on top of swim platform when an engine or generator is being operated
Carbon Monoxide can enter a cabin from the following sources:
- Exhaust gasses funneling back into the cabin due to wind direction known as the "Station Wagon Effect"
- Boats rafted together with one or more engines running
- Proximity to a dock or seawall with an engine running
- Hot water heater
- Generator running
- Galley stove
Proper elimination of Carbon Monoxide exhaust gases
It is essential to eliminate all carbon monoxide (CO) hazards. The following is a check list of potential CO producing areas that should be inspected on regular intervals;
- Make sure all exhaust clamps are in place and secure, free of corrosion, and in good repair.
- Look and listen for leaks in the exhaust system components, indicated by rust and or black streaking, water leaks, or corroded or cracked fittings. Pay extra attention to the cylinder head, exhaust manifold and riser and the threaded nipple between the two.
- Inspect all rubber exhaust hoses for wear, burned or cracked sections, and loosened clamps. All rubber exhaust hoses should be pliable and free of kinks.
- Make sure all ventilation systems are in good repair and are not obstructed, restricted, or punctured.
- Make sure gaps around engine room and exhaust system doors, hatches, and access panels are minimized to reduce the opportunity for carbon monoxide to enter the cabin.
- In many boats, especially double cabin vessels, the exhaust lines pass through the aft cabin on their way to the transom. If the exhaust lines run behind cabinetry, install inspection ports or removable panels in the cabinetry.
- Listen for any changes of sound in the exhaust system that would indicate a failing exhaust component.
Properly Maintain the Engine
Proper maintenance of the engine will reduce the carbon monoxide (CO) emissions. The following is a list of items to keep maintained to reduce the carbon monoxide emissions;
- Fuel System: Fuel that is contaminated, stale, or of the wrong octane number for the engine.
- Carburetors/Injectors: Dirty or clogged flame arrester, malfunctioning automatic choke or faulty adjustment of manual choke plate, worn flat needle valve and seat, high float level, incorrect idle mixture adjustment, and dirty or worn injectors.
- Ignition System: Fouled or worn spark plugs, worn points or improperly gapped points, shorted or opened circuit high tension spark plug cables, and incorrect timing.
- General Items: Worn piston rings and valves, low engine operating temperatures (cold-running engines increase carbon monoxide production, while engine operating at a higher end of the manufacturer's temperature range produce less CO), exhaust back-pressure caused by modifications to the exhaust system, and restricted engine compartment ventilation.
- Confirm that water flows from the exhaust to prevent overheating and burning through the exhaust system.
Other Sources of Carbon Monoxide
Gasoline engine exhaust is by far the most common, but not the only source of carbon monoxide. Portable electric generators should never be installed below deck. Because exhaust systems are rarely constructed of marine alloys they may rust through after only a brief exposure to a marine environment. Any flame-producing device needs to be used in a well ventilated area. Caution must be used when operating alcohol and propane heaters and stoves, catalytic heaters, oil and gasoline lamps, and charcoal grills because they consume oxygen. As oxygen levels in an enclosed space fall, fuel is incompletely burned and carbon monoxide is produced. When a normal blue flame becomes yellow and smoky it is an indicator that carbon monoxide is being produced. Open windows and or vents to prevent or correct this situation.
Teak Surfing
Although CO poisonings often have been reported to occur in enclosed and semi-enclosed environments, they can also occur in open-air environments. Teak Surfing entails individuals taking hold of the swim platform of a vessel while it is underway. After a large wake builds up, they let go of the platform and body surf. This puts the individual directly in the path of the vessel's exhaust where they breathe in dangerous levels of carbon monoxide. If that in itself is not dangerous enough, the individuals are also in a position that a slight miscalculation may throw them into a spinning propeller. It doesn't stop there, in order to Teak Surf you cannot wear a life jacket, and the two do not go together.
Wakesurfing should not be confused with Teak Surfing and the following video shows why.
Carbon Monoxide (CO) Detectors
While the first step of protecting yourself from CO poisoning is to stop it at its source you should still have a reliable CO detector. As of August 1, 1998 the organization that writes the voluntary standards for recreational boats, the American Boat and Yacht Council (ABYC), recommended that all boats with enclosed areas and a gasoline inboard engine of any type including gasoline generators have a CO detector installed. (Diesel engines were not included because they are much less likely to produce deadly levels of CO.) If your boat was built before August 1998 you will need to install one yourself.
Carbon Monoxide (CO) Detector Installation
CO detectors made prior to 1992 had a reputation for emitting false alarms. They would sound the alarm at the first detection of carbon monoxide gas. The frequent alarms several times a day would lead to the skipper to disarming them and rendering them totally useless. After 1992 CO manufacturers began making more technically advanced units that use "time-weighted averaging" of the CO concentration to greatly reduce the number of false alarms. The unit averages the detected carbon monoxide fumes over a period of time and will not sound unless they repeatedly detect CO. Make sure the alarm buzzer is loud enough to be heard over engine noise, background noise, etc.
A good marine grade CO detector should meet the requirements of ABYC A-24, Carbon Monoxide Detection Systems on Boats. The ABYC document states "Detectors shall be certified by an independent third party to meet the requirements of UL 2034, Single and Multiple Station Carbon Monoxide Detectors".
The location of the detector is not a concern because the gas is about the same weight as oxygen and tends to dissipate evenly in an area and isn't any more likely to be found down in low areas then up in the high areas. The best place to mount it is where it can be easily monitored and serviced. A CO detector should be installed in sleeping areas, main saloons, enclosed fly-bridges, and anywhere else people spend time. Avoid areas that are near hatches or doors where fresh air might distort readings and dead air spaces and corners.
Batteries should be installed properly and checked for good condition. Test the operation of the detector by pressing the test button. Remove the battery only to replace it with a new battery and never disable the CO detector, if the alarm sounds, identify the source of the alarm and rectify the situation.
Alarms on the new carbon monoxide detectors should not be discounted as the ones prior to 1992 were, the improved technology means that when a newer alarm sounds it should be investigated at once.
Effects of Carbon Monoxide exposure in Parts Per Million (PPM)
The carbon monoxide poison effect is a combination of the concentration of CO being inhaled (measured in parts per million [PPM]) and the length of time of the exposure to the carbon monoxide gas.
100 PPM Slight headache in two to three hours.
200 PPM Slight headache within two to three hours and a loss of judgment.
400 PPM Frontal headache within one to two hours.
800 PPM Dizziness, nausea, and convulsions within 45 minutes; insensible within 2 hours.
1,600 PPM Headache, dizziness and nausea within 20 minutes; death in less then 2 hours.
3,200 PPM Headache and dizziness within 10 minutes; death within 30 minutes.
6,400 PPM Headache and dizziness within one to two minutes; convulsions, respiratory arrest and death in less than 20 minutes.
12,800 PPM Unconsciousness after 2-3 breaths and death in less than three minutes.
Carbon Monoxide Concentrations at the Source
10,000 - 100,000 PPM Gasoline Engine
1,000 PPM Diesel Engine
Based on PPM on diesel engines verse the gasoline engines, the ABYC did not include diesel engines in there recommendation that all boats with enclosed areas and a gasoline inboard engine of any type including gasoline generators have a carbon monoxide detector installed, diesel engines have far less CO emissions then gasoline engines.
Carbon Monoxide (CO) that drifts in and out of a cabin can be dangerous, since the effects of carbon monoxide are cumulative and can build up gradually in a person's bloodstream over hours or even days before it reaches critical levels. Even if the person breathes fresh air periodically; the CO remains in the bloodstream. The half-life of carbon monoxide is approximately five hours, which means that it takes five hours for the level of CO in the blood to drop to half its level when exposure was terminated.
Recent research shows that the effects of carbon monoxide poisoning are transitory. 96 victims exposed to CO were studied and researchers found that over 25% showed evidence of brain damage 12 months after exposure. These long-term CO exposures can include apathy, memory loss, inattention, and depression.
Avoiding Carbon Monoxide (CO) Poisoning
- Inspect your exhaust systems regularly for any signs of leakage.
- Stay away from any activity on or under the swim platform when an engine is running and no teak surfing. In some areas there are laws, punishable by a fine, to operate a vessel's engine while a person is occupying or holding on to the swim platform, swim ladder, or teak surfing behind the motorized vessel. The law provides the exception of briefly assisting with docking, exiting or entering the vessel, or engaging in law enforcement or emergency rescue activities.
- Watch out for other boats that are running their engines around you. These idling boats can cause carbon monoxide build-up in the area.
- When running downwind set the course so the prevailing winds will dissipate the exhaust fumes.
- Keep forward facing hatches open, even in inclement weather, to allow fresh air circulation in living spaces.
- Educate all passengers about carbon monoxide poisoning so they no what the early CO poisoning signs are.
- Do not confuse carbon monoxide poisoning with seasickness, heat stress or intoxication. If someone on board complains of irritated eyes, headache, nausea, weakness or dizziness, immediately move the person to fresh air, investigate the cause and take corrective action. Seek medical attention if necessary.
- Install a CO detector in each cabin.
For more information please visit: http://www.uscgboating.org/safety/carbon_monoxide.aspx
Accidents from Carbon Monoxide Poisoning
Houseboat-Associated Carbon Monoxide Poisonings on Lake Powell — Arizona and Utah, 2000
Carbon-Monoxide Poisoning Resulting from Exposure to Ski-Boat Exhaust --- Georgia, June 2002
