The American Boat and Yacht Council (ABYC) changed its requirements for carbon monoxide (CO) detection systems in recent years. The updated Standard, A-24, Carbon Monoxide Detection Systems now requires virtually every boat with a cabin to have a carbon monoxide detector. Although CO detectors have been a requirement on boats with enclosed accommodation compartments for a long time, there was always an exception for diesel and outboard boats. The theory was that diesels produce less CO in their exhausts than gasoline engines, and outboard exhausts are essentially outside the boat.
While all new boats will be built to the standard, everyone should consider updating your vessel to comply with the new safety requirement. Many older diesel boats may have used the previous exception so you should confirm you have a modern working detector. There have been CO poisonings, some resulting in fatalities, in raft-up and slip situations where exhaust from a main engine idling or a generator running on a neighboring boat was pulled into an open hatch of a boat not required to carry CO detectors.
Since 2010, CO alarms have a built-in end-of-life alarm that lets you know with an audible and visual signal when it's time to replace it, usually after five or seven years. The first of these newer detectors are reaching the end of their life, so a lot of boat owners will start hearing the warning chirps that mean it's time to replace these alarms. If you have a detector that's older than seven years, replace it. New boats with accommodation spaces built to ABYC standards will come with CO alarms installed. Most boatbuilders who are members of the National Marine Manufacturing Association build to ABYC standards.
The ABYC defines “enclosed accommodations” as “one contiguous space, surrounded by permanent structure, that contains all of the following: a) designated sleeping accommodations; b) a galley area with sink; and c) a head compartment.” Even if your boat doesn’t fall under the above definition, if there’s an enclosed area you spend time in, please install a CO detector. Fireboy-Xintex (www.fireboy-xintex.com) and MTI Industries https://www.stamarine.com/carbon-monoxide-detectors.html, among others, sells sophisticated carbon monoxide detectors for marine use. They are more expensive than home detectors but they are designed specifically to the ABYC requirements. If you cook or heat with a gas fuel, consider installing a propane detector.
If you have a CO detector you are ahead of the game, but you should also consider the age. Check the date of manufacture and the recommended life before replacing. Most have a maximum of 10-year useful life.
Gasoline and Propane Vapor Detectors
Any boat with a gasoline fuel tank mounted below decks and/or a propane system needs a vapor detector.
BoatUS Marine Insurance has seen several explosions claims that occurred right after refueling. Gasoline, like other vapors, has an "upper explosive limit," or UEL. Too high a concentration means it can't ignite. A leaking fuel-fill hose can allow gas to collect in the bilge, making vapor concentration too high to ignite. This prevents engines from starting because there are too many gas fumes and not enough air to support combustion inside the engine. But as fresh air gets mixed with the vapors, say after opening the engine cover, the fumes become less concentrated than the UEL, and a spark from a faulty starter or bilge-pump switch can ignite the fumes in a spectacular way. If your boat refuses to start right after fueling, check for a gasoline spill.
Also known as fume sniffers, vapor detectors monitor for flammable gases. Propane and gasoline fumes have to mix with air before they'll ignite. These detectors analyze the air around them and sound off long before that concentration is high enough to explode. This air/vapor mixture is called the "lower explosive limit," or LEL, and varies with the type of vapors. For example, gasoline fumes will explode at about 1.5 percent by volume of air; vapor detectors will sound an alarm when they sense the level is about 20 percent of that, giving you time to find the problem before it gets out of hand.
Vapor alarms should be mounted in the engine-space bilge, just above the slosh height of bilge water. Mount the sensor away from the hottest parts of the engine, such as manifolds. Vapor alarms are almost always hard-wired to the boat's 12-volt DC system. Usually, the unit has a control head mounted at the helm that will sound when dangerous fumes are detected in the bilge. The wire that connects the sensor to the head unit typically can't be cut, because the manufacturer has calibrated its length. Some vapor detectors can turn on the bilge blower when they detect a buildup, a smart option. The blower, of course, must be ignition protected. Look for an alarm that is UL 2034 listed. Vapor alarms should be tested monthly, using the manufacturer's procedure. Replace them after no more than five years, or right away if they become submerged.
If the alarm sounds, shut down the engine, turn off the battery switch, open the engine compartment, and look for the source of a gasoline leak. If you have a propane system, turn off the valve at the tank, open hatches, and air the boat. For a small gasoline leak that can be safely repaired, a bilge blower can help rid the engine space of vapors, but it won't remove liquid gasoline. If you're on the water, there's likely nothing you can do about a ruptured fuel tank that's spewing gas into the bilge except call for help; a cellphone is a better choice in this case than a VHF, which isn't required to be ignition-protected. A handheld VHF used away from the spill is safer still. Flares are a bad idea. Have all crew don life jackets, and move everyone to the forward part of the boat; as a last resort, the crew can take to the water, but don't go far — someone who happens along won't know your boat is full of explosive fumes. At the dock, larger quantities of spilled gas should be dealt with by pros. Get everyone off the boat and call 911. Don't operate anything electrical, including the blower; it won't eliminate spilled gas.
While there are apparently no regulations regarding smoke detectors on boats, LGYC recommends that everyone consider adding smoke detectors to their vessel. There has been loss of life in the area from an electrical fire that would have been detected by a smoke detector and potentially saving the vessel occupants. Rather than using a detector with replaceable batteries, consider the new lithium ion battery detectors that are good for 10 years and it eliminates remembering to change the batteries. Just pick up one of the many smoke alarm models on the market (RV offerings, which typically run from $20 and up, are preferable) and stick them in your boat. Install alarms on every level of your vessel much like you would in your home.