For example, just a few days before I wrote this (December, 2008) 29 people were treated for CO poisoning at a warehouse, simply because they closed the big doors to keep the place warm during a snowstorm.  They were also using fork lifts that had internal combustion engines inside the warehouse.  The people who closed the door probably didn't even consider what the consequences would be.

So what has this to do with boats?  In most of the world where winters are frigid, few people go boating.  So the problem is probably at it's low point in the winter for boats.  But, in the summer, especially in areas that are hot and humid, the opposite problem, keeping cool, exists. This is especially so on boats, particularly houseboats, but it is not confined to them.

CO poisoning on boats is not a new problem. The problem has become worse because boats have gotten better.  Up until the 1960's, when fiberglass boat building really took off and boats became mass produced, boats were notoriously cold, drafty and damp. When boats began to be mass produced, manufacturers ramped up the comfort factor, making them warmer and less drafty. This meant tightening up the interior with few gaps in compartment bulkheads, insulating hulls and overheads and seriously improving the look and style of the interiors and exteriors.  All this meant less ventilation.  So CO is more easily trapped inside the boat. However, any gaps in bulkheads, such as around wires and pipes, allow the CO to get out of the engine room and into passenger areas. 

Also engine rooms are tighter and better insulated to reduce noise.  This also traps CO.  Boats also have much larger and more powerful gasoline engines which need lots of air to run properly. When they don't get enough air they produce more CO.  Styling decisions, to make boats more marketable, have also resulted in larger accommodations and designs that tend to create low pressure areas behind the boat that suck in exhaust, allowing it to enter through drains and vents. Styling has also resulted in placing exhaust outlets below swim platforms and on flat transoms, another way to trap CO. 

Another factor contributing to more CO was the increased use of permanently installed generators.  Many of these were gasoline powered (most are diesel now) and  are typically used when the boat is at anchor or tied up to the dock, to power air conditioners and a plethora of other electrical appliances such as refrigerators, televisions, computers and even electric stoves.  The exhaust from these generators has been a major culprit in CO deaths.

What to do: The first, and most important step is education.  Boat builders must provide educational material on CO for the customers who buy their boats. Most of this is free and available from NMMA, the US Coast Guard, the Consumer Product Safety Commission and other organizations.  Why?  To prevent deaths which often wipe out whole families. It also reduces the manufacturer's exposure to liability and to having their good name destroyed. 

Next is to design the boat to reduce the possibility of CO entering the boat.  ABYC has standards and technical reports that provide ways to reduce CO.  This includes eliminating holes in bulkheads, providing adequate ventilation in engine rooms, and designing exhaust systems that direct CO away from the boat.  Also, designing the interior and exterior of the boat to reduce areas that would tend to suck in CO is extremely important. It is not as easy as it sounds. 

Design Considerations:
Where is the engine exhaust outlet? 
Is it under or on the swim platform?
Where are drains and vents placed in respect to exhaust outlets?
Where are the engine air intakes/outlets positioned in relation to the exhaust?
Is the engine getting enough air?
Are interior bulkheads watertight and air tight?
Are accommodations adequately ventilated?
Is there a path for air through the boat to vent CO out of the boat?

Installing marine carbon monoxide detectors is also crucial.  Even after all the above has been done, conditions can exist that allow CO to get in the boat.  CO detectors will give the occupants adequate warning to get out and ventilate the boat. 

Certainly last but not least is the engine.  Provide information to the customer about why it is so important to keep the engine properly tuned.  It goes way beyond getting the most efficiency and economy. Provide maintenance procedures in the owners manual  that include engine maintenance, inspecting exhaust systems, changing exhaust hoses when needed, and not running engines when not necessary. Provide an owners manual for the generator with the same type of information.

In addition to the above you can place CO warning labels on the boat in prominent places such as the engine room hatch or door. Placing a warning label on swim platforms is very important. Provide emergency medical procedures in the owners manual in the case CO does get into the boat, and how to get help. 

Links to sites about Carbon Monoxide Poisoning:
Carbon Monoxide Kills  
USCG On Carbon Monoxide
California Boating And Waterways on Carbon Monoxide
Carbon Monoxide Warning Pamphlet by NMMA USCG and ABYC
ConsumerReports.org - Carbon monoxide clinical data on carbon monoxide poisoning. 
Houseboat-Associated Carbon Monoxide Poisonings on Lake Powell --- Arizona and Utah, 2000 : Center for Disease Control
Carbon Monoxide Pamphlet Boating Sidekicks
Carbon Monoxide Alert David Pascoe on Yacht Survey .com
ABYC Standards. Information On Carbon Monoxide From ABYC. Look for: TH-22 EDUCATIONAL INFORMATION ABOUT CARBON MONOXIDE.
Carbon Monoxide Safety A site by Qualified Hardware with many great links for information on CO.

References about Dealing with Carbon Monoxide: (At the top of each link page select CONTENTS and look for the subject title in the menu.)Professional Boatbuilder #107 Jun/Jul 2007 Reducing the Risk
Professional Boatbuilder #109 Oct/Nov 2007 Venting The Boat Part 1
Professional Boatbuilder #110 Dec/Jan 2008 Venting The Boat Part 2
Professional Boatbuilder #111 Feb/Mar 2008 The Dry Exhaust Part 1
Professional Boatbuilder #112 Apr/May 2008 The Dry Exhaust Part 2

Links to sites referenced above.
Boat Safety Blog http://newboatbuilders.blogspot.com
Portable Generators http://newboatbuilders.com/docs/portable.pdf
National Marine Manufacturers Assoc, http://www.nmma.org/search.aspx?q=carbon+monoxide&x=11&y=5
US Coast Guard on carbon Monoxide http://www.uscgboating.org/safety/carbon_monoxide.aspx
American Boat and Yacht Council Downloadable Standards http://store.abycinc.org/merchant.mvc?Screen=CTGY&Store_Code=ABYC&Category_Code=DL_STANDARDS
Carbon Monoxide Kills http://www.carbonmonoxidekills.com/60/carbon_monoxide_board/
California Boating and Waterways http://www.dbw.ca.gov/BoaterInfo/CODanger.aspx
Consumer Reports on CO and Boats http://www.consumerreports.org/health/resources/pdf/clinical-guidelines/sr-acute-carbon-monoxide-poisoning-2103.pdf
Houseboat-Associated Carbon Monoxide Poisonings on Lake Powell --- Arizona and Utah, 2000 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4949a1.htm
Carbon Monoxide Pamphlet Boating Sidekicks http://www.boatingsidekicks.com/cobro/cobrochure.htm
Carbon Monoxide Alert David Pascoe on Yacht Survey .com http://www.yachtsurvey.com/carbon_monoxide_alert.htm
Professional Boatbuilder Digital Issues http://www.proboat.com/digital-issues.html

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