Carbon monoxide - Quickly finding, diagnosing, and fixing

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Guide to Carbon monoxide

Simply owning a combustion analyzer is not enough to keep you safe. You must also understand how to use it properly. Many people operate combustion analyzers without truly understanding what the readings indicate. Before using the equipment, learn how to interpret the different readings and make any necessary adjustments that will maintain the analyzer and prevent false readings.

Carbon monoxide

Poisonous Carbon monoxide can Build Up In a Boat. Gasoline-powered engines on vessels, including onboard generators, produce CO gas, a colorless and odorless gas that can poison or kill boater who breathes too much of it. This venting poses a danger of CO poisoning on the rear water platform or swim deck.

Carbon monoxide is a common danger.

In fact: At slow speeds traveling or idling in the dock
can cause or idling in the water to build up in a boats cockpit and cabin, Also the Wind from the aft section of the powerboat can also increase this buildup of Carbon monoxide levels.

Quickly finding, diagnosing, and fixing a carbon monoxide leak will save lives. However, these steps demand training. Learning how to use acombustion detector accurately can save lives.

The manufacturer of your combustion detector is the obvious resource for understanding how readings should be interpreted. These instructions, however, are not always very specific, particularly when you have to make adjustments or correct any problems. There are too many variables for manufacturers to address.

For example, they cannot explain the differences in oil-fired and gas-fired equipment.

Anyone who wants to gain expertise in the use of combustion analyzers should look into taking a course with an experienced professional. Research different CO trainers in your area to find someone who understands how different analyzers operate and has actual field experience. The ability to repair malfunctioning combustion analyzers is something else you might want to consider learning.

carbon monoxide in the United States

Each year, carbon monoxide poisoning kills 500 people in the US. According to the Center for Disease Control, over 10,000 are made ill from carbon monoxide poisoning. Many of these people suffer permanent damage to their health.

The Importance of Using A Combustion Analyzer Properly

Numerous household appliances can release carbon monoxide. This gas can be found anywhere, and there is no safe level. Exposure can occur from engines, generators, furnaces, water heaters, boilers, cars, lawnmowers, grilling equipment, space heaters, generators, wood-burning stoves or fireplaces, gas-burning stoves or fireplaces, gas ranges and self-cleaning ovens. There needs to be a minimum of one carbon monoxide detector in every home with electric appliances, just in case the dangerous gas does build up.


Everyone needs to be familiar with the symptoms associated with exposure to carbon monoxide.

Chronic symptoms that affect multiple members of a crew, household could indicate long-term CO exposure.

Common symptoms include: headache, fatigue, nausea, vomiting, muscle pain, diarrhea, confusion, memory loss, chest pain, accelerated heart beat, fast breathing, shortness of breath, along with changes in vision, hearing, touch, taste or smell.

Anyone who experiences these symptoms should use a combustion analyzer to find the source of the carbon monoxide leak.

Even low levels of carbon monoxide are dangerous. Over time, physical and mental health problems have been linked to exposure to CO levels as low as 10 ppm. Carbon monoxide levels that rise to 35 ppm or more require firefighters to put on oxygen masks.

It is recommended that people with chronic health conditions use low-level carbon monoxide monitors. Small amounts of carbon monoxide are so dangerous that 80 percent of the appliances gas companies red-tag have CO levels of 10 ppm or higher, according to the Southern Gas Associations recent survey.

Accidental carbon monoxide poisoning causes too many deaths and permanent health problems in the United States. Fortunately, carbon monoxide poisoning can be prevented by properly using combustion analyzers to test.

Alarms and Detectors

Carbon monoxide

Carbon monoxide (CO) is released from many of your on board systems such as the engine exhaust, the galley range, grills, portable space heaters and any defective exhaust systems on board, not only the engine, but the generator as well any system that produces fuel combustion. CO is a colorless, odorless vapor that does not sink to the bilge but tends to hangin the atmosphere where you can breathe it, resulting in dizziness, sleepiness, nausea and even death. Minimizing the danger of CO poisoning is accomplished by providing good active and passive ventilation to all combustion devicesand inspecting your exhaust systems regularly.

Having systems on board that use gasoline, propane (LPG) or compressed natural gas (CNG) provides the potential for harmful vapors being released into your boat. These vapors can cause explosions if ignited and also carbon monoxide poisoning, the fire itself will also release dangerous vapors and smoke.

Gasoline vapors

Gasoline vapors are also heavier than air and will sink to the bottom of the bilge and lockers. These vapors are also highly explosive if ignited. While current American Boat & Yacht Council (ABYC) standards do as much as possible to eliminate poor construction and installation methods, there are system maintenance items that should be performed on a regular basis to avoid gasoline fuel and vapor leaks. By periodically checking all connections, fittings, hoses and tanks for leaks, you can minimize the potential of an explosion on your boat. Following safety guidelines when filling the boat’s tanks at the fuel dock also goes a long way in preventing gasoline-based explosions.


LPG is heavier than air, will sink to the bilge and the bottoms of lockers, and if the vapors are not allowed to escape and are ignited, they’ll cause an explosion. CNG vapors are lighter than air and if removed by overhead ventilation the vapors will dissipate into the atmosphere. If the vapor is not removed from the cabin it will mix with air and become explosive if ignited.

Both LPG and CNG have an odorant added which helps detect leaks. If, when boarding and opening up your boat, you smell an unusual sweet odor and have either LPG or CNG on board, immediately open all lockers, bilge boards, cabin ports and hatches. Air the boat out well before turning on any electrical appliances in the boat or any other ignition source

Most fume detectors will sound an alarm if the explosive vapors reach the 10 to 20 percent level of the concentration required for an explosion.

Good detectors will have remote sensors. These sensors can be placed in the areas where explosive vapors will accumulate and some will have multiple sensors for monitoring more than one area.

There are currently CO, LPG and CNG, gasoline, smoke, fire and heat detectors available on the market made for installation in boats. The UL listing should be on the device itself and not just the packaging. Alarms are activated by the concentration of the vapor, smoke or heat in the area being monitored.

The Fireboy-Xintex Model CMD-4MR-RLY Listed for Marine use

Fireboy-Xintex Model CMD-4MR-RLY

Before you buy

Pay attention to the manufacturing date. They have a 5-10 year life span. They all do the same thing. Same with fire extinguishers. If you buy from Walmart or a box store, even west marine. Open the box and check the date.

The 12 VDC detector is the most advanced detector that features multiple location warning, allowing up to six CO detectors to be relayed in series. (

CO alarms can also monitor the concentration level relative to the length of time the vapor is in the space. When reading the manufacturer’s specifications, an important term to understand is LEL or Lower Explosive Level. This is the lowest percentage or level of vapor concentration at which an explosion will occur and the device’s sensitivity level is described as a percentage of this level, - 20 percent is good and 10 percent is better.

Your unit should also have an internal self test which automatically tests the sensor(s) and connecting wires. This self test does not check the sensor itself however, and yearly recalibration may be required. LPG detectors should have an automatic shut-off for the electrically operated solenoid valve, in addition to the manual shut off switch.

Another alarm you should consider having on your boat is a bilge high-water alarm. Excessive amounts of water entering the bilge indicates leaks and these can be from any of the plumbing systems or the thru-hulls. Knowing there’s excessive water in the bilge before it comes up over the floor boards can help you contain a potential emergency and locate the problem.

There are multi-use sensors available too. For instance gasoline fume detectors that also detect propane, alcohol, hydrogen from batteries, and other explosive vapors. Combination fume, flood and fire detectors and combination smoke and CO detectors are also available.

These alarms should be UL listed for the multiple vapors or smoke detection the manufacturer’s claims represent.

ABYC recommends installing CO detectors if your boat has enclosed sleeping spaces on board, inboard gasoline engine(s), or gasoline generator(s) and they provide guidelines for locating CO, gasoline and LPG/CNG sensors. Other organizations, such as the National Fire Protection Association (NFPA), also provide guidelines for locating smoke and heat detectors.

In addition to the safety and peace of mind these detectors give you and your crew, your insurance company may give rate discounts for having some, if not all of these detectors on board.

There is a unseen problem facing boaters, Carbon Monoxide Poisoning.

Boats have two problems with Carbon Monoxide Poisoning, an enclosed engine and poor ventilation when at dock. this problem happens in more than one way.

1) when running on "plane" for a while and then coming to an idle to anchor or dock, the air flow in the bilge stops and gas engines will always "weep" exhaust (drive your car on the highway, park it, wait a few minutes, lift the hood and a smell of exhaust will hit you). I a boat these fumes are trapped in the bilge, and the bilge goes stem to stern. The fumes will be present and filter through the boat. The Carbon Monoxide in these fumes can't be seen and has no oder, yet they are DEADLY. To prevent this turn the blowers on when you start to come off plane. Once at anchor or dock lift all hatches and open all windows, do not put the AC on right away. A 15 min wait is recommended. Also leave the blowers on for the 15 min.

2) When at dock boats are usually backed in so boats are stern to stern. A couple of years ago two people were sleeping in their cuddy cabin. The cabin doors were wide open but the hatch was closed. The boat behind them was running while the owner was doing some repair. Carbon Monoxide went into the cuddy cabin and was trapped with no way out.
Your own boat idling with a following wind could cause the same problem.

3) When at anchor and guests are swimming, NEVER RUN THE GENNY. The fumes will gather fro the water up six to eight inches. Exactly where the swimmers noses are.

Always do two things, make sure there is proper ventilation and get a Carbon Monoxide Alarm. I have one and most of my old salt fellow boaters have them.