Safe With Sound

The most important alarm on

your boat may be a CO detector

Choosing and installing a

carbon monoxide detector

While shouts of “Fire!” “Man overboard!” and “We’re out of ice!” are all cries of alarm boat enthusiasts dread to hear, there’s one alarm many won’t hear that could wind up costing them their lives—the wail of a carbon monoxide detector. Too often this isn’t because the danger doesn’t exist, but rather because there’s no detector installed to begin with. Many of the stories in the news concerning boats and carbon monoxide end badly, but it doesn’t have to be that way. Let’s take a look at how to protect yourself and everyone else onboard by installing a carbon monoxide detector.

Know thy enemy–what is carbon

monoxide and why can it be deadly?

Carbon monoxide (CO) is a potentially lethal gas produced when burning any carbon-based fuel such as gasoline, diesel, propane, or wood. The most common source of carbon monoxide is exhaust from gasoline or diesel engines, however any open flame device—cooking ranges, heaters, or grills—can be guilty of producing deadly amounts of CO.
Carbon monoxide mixes easily with air, meaning it readily travels throughout a boat’s interior spaces. It is easily absorbed into the bloodstream, where it displaces oxygen in the body and can lead to carbon monoxide poisoning.
Exposure to even small amounts can be lethal, as the effects of CO are cumulative and can build up gradually in a person’s bloodstream for hours or even days before reaching critical levels.  How quickly this occurs is dependent on the concentration of CO being inhaled (measured in parts per million) and the duration of exposure. Common signs of CO poisoning include headaches, dizziness, weakness, drowsiness, and nausea–symptoms that can all too easily be attributed to sea sickness, alcohol consumption or too much sun exposure.

CO detectors

Since carbon monoxide (unlike the smoke generated by a fire) is colorless, tasteless and odorless, the only reliable way to guard against it is with the installation of a CO detector.  The American Boat and Yacht Council (ABYC) has called for the installation of CO detectors on all boats with enclosed accommodation areas and a gasoline generator or inboard gasoline propulsion engine since 1998.
ABYC exempts diesel engines from this requirement and while it’s true they produce less CO than gasoline engines, my personal recommendation is that detectors be installed aboard all vessels with sleeping accommodations. CO can easily be generated by other sources onboard or even introduced from nearby boats via the ventilation system, which is especially true of boats running air conditioning.

Choosing a CO detector

There are a few things you should know before heading out to purchase a CO detector. The first impulse for many boaters is to buy a home-type CO detector, but they typically don’t meet the construction requirements for marine grade units (such as Underwriters Laboratories standard 1524) and are not recommended.
Marine CO detectors can be either battery powered (the 9-volt type) or hardwired. The obvious benefit of battery-powered units is that they can be installed anywhere without the need for wiring, however this lack of an external power supply can also be a disadvantage from a reliability standpoint.  Self-test the unit weekly and replace the batteries regularly as per the manufacturer.
Hardwired marine units are powered by the vessel’s 12- or 24-volt DC power system.  Those designed for residential or commercial installations utilize 120VAC, which may not always be available while cruising. Power for wired CO detectors must be provided via an appropriate fuse or circuit breaker, keeping in mind that they should also be wired to remain energized at all times.  In other words, they should be fed from the “hot” side of the battery switch to prevent them from being accidentally shut-off.
Wired units can also offer more advanced features, such as automatic generator shutdown in the event CO is detected.  Visit the MariTech Industries (maritechsafety.com/cops/asp) and fireboy-Xintex (fireboy-xintex.com/co-detectors.html) Web sites for additional information.
CO detectors gained a bad reputation in the past for generating numerous false alarms. Modern units use “time-weighted averaging” to determine the amount of CO present over a period of a few minutes rather than at one point in time, greatly reducing the number of false alarms.

Location, location, location

ABYC does not state specifically where a CO detector should be located on your vessel, however it does provide some general guidelines. First of all, they must be located to monitor the atmosphere in the main cabin and each sleeping area. Enclosed helms (flying bridges for example) or any other place people tend to congregate are good candidates for detectors as well, which depending on your boat’s configuration, may require the installation of multiple units, or sensors if part of a system.
Choose a location that both protects the detector from rain, spray, sunlight, etc., and avoids what ABYC calls “dilution of sampled air” which could occur near hatches, ports or forced ventilation openings. Locations containing “dead air” spaces should be avoided as well. Unlike LPG or gasoline vapors, which are heavier than air, CO has roughly the same weight as oxygen, meaning detector placement is not limited to high or low areas of the cabin. As such, choose a location that is roughly eye level, to easily monitor detector meters or warning lights.
Finally, CO detectors have a limited lifespan. Detectors or system sensors will typically need to be replaced every five years, however this varies between units and can be as soon as one year from date of purchase. Check with the manufacturer and verify the recommended replacement intervals prior to purchase and installation.