Lessons Learned – by Pat Carson
What Is Your Carboxyhemoglobin Level?
Carboxyhemoglobin (COHb). I thought the same thing when I read, or tried to read, the word, but we should all know what it is – the concentration of Carbon Monoxide, CO, in your bloodstream is expressed as COHb.
How Much CO Is Too Much?
Normally when oxygen is inhaled into your lungs it combines with hemoglobin in the red cells of your blood to form oxyhemoglobin. The oxygen is then transported throughout your body by your arteries and capillaries, where it disassociates from the hemoglobin and oxygenates the cells of your tissues and organs including your brain. The deoxygenated hemoglobin then returns through your veins to your lungs, where it is combines with more oxygen and the cycle repeats. When carbon monoxide is inhaled the CO combines with your hemoglobin to form carboxyhemoglobin. The COHb bond is over 200 times stronger than oxygen’s bond with your hemoglobin and therefore the CO effectively puts your hemoglobin out of commission and deprives your body of the oxygen it needs to survive. The strong COHb bond explains why even very tiny concentrations of carbon monoxide can poison you slowly over a period of several hours, and why it may take a long, long time for your body to eliminate CO buildups from your bloodstream. As the CO level in your blood increases, the amount of oxygen transported to your body’s cells decreases. It is this oxygen deprivation that makes CO so deadly. Sensitive parts of your body like your nervous system, brain, heart, and lungs suffer the most from this lack of oxygen. Symptoms of mild CO poisoning include headache, fatigue, dizziness, vision problems – particularly double vision, nausea, and increased pulse and respiration. Unfortunately, these symptoms are often attributed to flu, indigestion, or the common cold. At higher levels of COHb saturation, you may suffer difficulty in breathing, loss of consciousness, collapse, convulsions, coma, and even death.
Depending on whom you ask, OSHA (the U.S. Occupational Safety and Health Administration) originally established a maximum safe limit for continuous exposure to CO in the workplace of 35 PPM (parts per million), then later raised it to 50 PPM under pressure from industry. On the other hand, the U.S. Environmental Protection Agency (EPA) issues a health hazard alert when the outdoor concentration of CO rises above 9 PPM for an extended period or above 35 PPM for one hour.
Breathing CO concentrations of:
200 PPM will result in slight headaches within two to three hours.
400 PPM results in frontal headaches within one to two hours.
800 PPM will see dizziness, nausea, and convulsions within 45 minutes. Insensible within two hours.
1,600 PPM is lethal with initial headache. Dizziness and nausea within 20 minutes. Death within 30 minutes.
3,200 PPM will cause headache and dizziness within five minutes. Death within 30 minutes.
6,400 PPM results in headache and dizziness within one to two minutes. Death in less than 15 minutes.
12,800 PPM – Death in less than three minutes.
Just how sick you will get from CO exposure varies greatly from person to person. Depending on age, overall health, the concentration of CO, and the duration of exposure, high concentrations can cause incapacitation within minutes, but low concentrations can still be extremely dangerous if you are exposed for a period of hours. As CO continues to be inhaled, the percentage of COHb gets higher and higher, and you get sicker and sicker. Your eyes are particularly vulnerable to the effects of CO poisoning, and permanent damage can easily occur. The body’s normal level of COHb is between 1% and 2%, however cigarette smoking will normally produce a COHb saturation of 3% to 10%. Given the variability level of COHb due to CO levels in the environment an upper limit for nonsmokers is 3% and for heavy smokers is 10%. Breathing air with a CO concentration of 70 PPM will result in a COHb concentration of 10%. To maintain COHb below 2.5% all the time CO exposure cannot exceed 10 ppm.
CO that drifts in and out of a boats cabin can be dangerous, since the effects of CO are cumulative and can build up gradually in a person’s bloodstream over hours or even days before it reaches critical levels. This is true even if when the person breathes fresh air periodically since the CO remains in the bloodstream.
How quickly the CO builds up is a factor of the concentration of the gas being inhaled and the duration of the exposure. The half-life of CO is approximately five hours, which means that it takes five hours for the level of CO in the blood to drop to half its level when exposure terminates. There is also some recent research that challenges traditional thinking that the effects of CO poisoning are transitory. Studying 96 victims for one year beyond their exposure, researchers found over 25% showed evidence of brain damage 12 months after exposure. These long-term CO injuries can include apathy, memory loss, inattention, and depression.
CO Concentration At The Source
Gasoline Engine 10,000 – 100,000 PPM;
Diesel Engine 1,000 PPM.
Carbon Monoxide is a colorless, odorless, invisible gas created when fossil fuels are burned incompletely in engines, generators, and even propane cook tops. As the boat owner and skipper, you should be diligent in educating each passenger about the signs and symptoms of Carbon Monoxide poising. When doing the engine room checks, be sure to look at the exhaust system components taking a particularly close look at the rubber exhaust hoses for signs of cracking or burning. Proper water flow is required to keep the exhaust system cool so always check for proper water flow out the exhaust. Test the operation of the CO detectors regularly, if they use batteries be certain to change them as recommended by the manufacturer. In addition, do not forget the generator; it has a similar exhaust system as the main engines.
While it is true that diesel engines do not produce a lethal concentration of CO, diesel exhaust is a mixture containing over 450 different components, including vapors and fine particles. Over 40 chemicals in diesel exhaust are considered toxic air contaminants by the State of California. Exposure to this mixture may result in cancer, exacerbation of asthma, and other health problems.
One reason that ABYC may have been slow to recommend the use of CO detectors may be their reputation in the past for periodically emitting unnerving false alarms. You could almost count on a CO detector to sound whenever they detected even the slightest trace of CO. Since a whiff or two of CO is likely to drift into your boats cabin several times a day, the frequent alarms were an ongoing nuisance. After 1992 manufacturers began making more technically advanced units that use time weighted averaging to greatly reduce the number of alarms. By averaging the CO over a period of a few minutes, these second-generation alarms will not sound unless they repeatedly detect CO. The microprocessor in a modern CO detector runs the air sample levels through a timeweighted algorithm to determine when a person’s COHb level would begin to be dangerous. For example, 70 ppm of CO over four hours would result in an approximately 10% level of COHb and would be the point at which an alarm would first sound. However, at 400 ppm, COHb levels reached 10% in only fifteen minutes, and the alarm would also sound.
Modern units designed for the marine environment can even do things like disengage the generator if CO is detected and can be connected together so that when one detector alarms, all connected detectors will alarm to alert boat inhabitants in other locations to the presence of carbon monoxide. Considering using a household grade CO detector note that marine units are designed for the wider temperatures seen on vessels and are more immune to the constant vibration not seen in the average home.
ABYC, American Boat Yacht Council, A-24 standard recommends that any vessel that has a galley, sleeping accommodations, or an enclosed head should have CO detectors installed. CO is about the same weight as oxygen, tends to dissipate evenly in an area, and is not any more likely to be found up near the ceiling or down by the cabin sole. Placement is easy because many are powered by a 9-volt battery. CO mixes well with air, and there is usually circulation on a boat, so positioning them is not overly critical. Mount them where you can see them, not in a corner or near a low shelf or berth because a blanket or jacket could inadvertently cover them. As a practical matter, placing an alarm at eye level allows you to easily monitor any meters or warning lights on a unit. Sleeping areas, the main saloon, an enclosed flybridge, and anywhere else people spend time are candidates for a CO detector however areas that should be avoided include near hatches or doors where fresh air might distort readings. While the older alarms were often a nuisance, the improved technology means that when a newer alarm sounds it should be immediately investigated.
Effective in 2010 UL, Underwriters Laboratories, mandated a five-year end of life on carbon monoxide detectors. Any vessel with CO detectors manufactured prior to 2010 should be replaced with modern devices that meet the current UL2034 standards. According the Fireboy-Xintex technical bulletin these new and safer units will:
“Approximately 4 years and 11 months after activation your Fireboy-Xintex carbon monoxide detector will enter the EOL (End-of-Life) phase of its existence. There will be both an audible alert (intermittent beep once every 30 seconds) and a visual alert (green LED OFF and Red LED ON). During the initial warning period, depressing the Test/Silence button located on the right hand side of the CO detector will silence the EOL Alarm for 3 days at a time. These alarm features are designed to remind the owner to replace the detector before its five-year life span expires. Once the detector has reached its five year threshold, the detector will shift to an alarm that cannot be manually silenced, At that point, a new Fireboy-Xintex Carbon Monoxide Detector will need to be purchased, the unit will still detect the presence of CO and alarm appropriately.”
According to the U.S. Coast Guard’s report on 2019 Recreational Boating Statistics, carbon monoxide poisoning ranks fourth in the top five known causes of death among boaters and is the most common cause of illness and death by poisoning in boaters. An earlier joint study conducted by the U.S. National Park Service, the National Institute for Occupational Safety and Health, and the U.S. Coast Guard on carbon monoxide dangers associated with boating, particularly houseboats, revealed that more than 800 people have been poisoned by boating related carbon monoxide in the last 15 years, with over 140 of these poisonings resulting in fatalities. Carbon monoxide is one of the most dangerous poisons because often boaters do not realize that it is present until it is too late. It is important to educate yourself about the dangers of carbon monoxide poisoning so that you can protect yourself and your fellow boaters.
Install and maintain a working CO detector listed by Underwriters’ Laboratories (UL) as appropriate for marine use inside the boat. Properly install and maintain all fuel-burning engines and appliances. Educate all passengers about the signs and symptoms of CO poisoning. Do not swim or play in areas where an engine is running. And remember it is not just your boats engines, exhaust from a nearby vessel can send CO into the cabin and cockpit of your boat. Do not dock, anchor, or raft within 20 feet of other boats that have engines or generators running.
You and your passengers are at increased risk for carbon monoxide poisoning if you operate a vessel that is fitted with a rear vented exhaust system, if you regularly travel at slow speeds or idle in the water, operate your boat at a high bow angle, overload or improperly load your boat, or own a boat with an opening that draws in exhaust fumes.
If you think a person on your boat has CO poisoning move him or her to fresh air right away and contact the nearest emergency services. If you have oxygen on board and are knowledgeable in its use, give the victim oxygen.
Remember that with all of the other maintenance tasks on our recreational vessels CO detectors are a maintenance item as well, it is best not to ignore their silent protection.
Until next month please keep those letters coming and check that your CO detectors are not out of date and are functioning properly. I just received my new CO detectors and have the port and cigar waiting for me as soon as I replace these old devices more modern ones.
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