Carbon Monoxide Alarms

Carbon monoxide detectors can save your life.

June 17, 2011

You can’t smell it, you can’t see it, and you can’t taste it, but it can kill you — or at the very least make you really sick. It’s carbon monoxide (CO), and it’s present whenever you fire up the engine, genset, stove or barbecue. It can creep into your living space from the guy docked in the next slip, so you need one even if you don’t have a generator.

The best way to alert yourself to the presence of CO is to install one or more carbon monoxide alarms in any enclosed or semienclosed area, wherever people congregate or sleep. This would include an enclosed flying bridge. What should you look for in an effective alarm?

Saltwater Tough
First, avoid residential alarms. While marine units may be more expensive, they are built to withstand the rigors of a marine environment. Plus, price should not be an issue when your life is at stake. Look for units that are UL listed for marine use.


Most boaters opt for a hard-wired 12-volt DC unit. There’s rarely a time when the ship’s electric system will not be available. A better choice might be a combination hard-wired/battery-backup unit, in case boat power fails. Pure battery-operated alarms are not recommended since battery life is unpredictable and they are easy to disable by removing the batteries.

It’s important to know that CO can spike momentarily on board whenever an engine/genset starts or a stove or oven is lit. Time-weighted averaging takes the spike and averages it over a preprogrammed length of time, and the unit typically will trip only when the average over time reaches 70 parts per million or higher. Time-weighting reduces nuisance false alarms from momentary spikes.

A Couple of Nice Extras
Here are a few other notable features present on some alarm systems:


Genset Cutoff — Some alarms have the ability to shut down a generator whenever high CO accumulation is detected. If you have a genset, it’s a great feature; if you don’t, it’s not worth the extra cost.

The Principles of Generator Safety Aboard Boats

Multiple Location Alert — With this feature, you can hook up a number of alarms in a series and, when one unit trips, all units sound.


Memory Recall — This allows boaters, first responders or boat mechanics to verify the level of CO that was detected, and it shows when the alarm was tripped by CO and not outgassing.

Finally, keep in mind that the sensors in CO alarms have a specific life cycle. The entire unit should be replaced at least every five years.


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