Marine CO Poisoning

Links to web pages regarding carbon monoxide and boating issues.
Hello George,

I was out on a dive boat this weekend and used your CO detector to check my tank fills which had 0 ppm of CO in them. I put the detector in my duffle bag and loaded it onto the dive boat and away we went.

Well, about twenty minutes into the ride to the dive site I start to hear a chirp from my bag. I open it up and see that the detector says 70 ppm of CO. I was sitting about a yard forward of the stern.  I then put it in the fresh air off the front of the boat and it went to zero. I then entered the covered pilot house and 35 ppm of CO.

I have no idea how high it was at the transom but likely very high as this boat had a swim board and rear exhaust. I think people call this effect the ‘station wagon’ effect as we were traveling about 30 mph.

When I got home I had a look on the Internet and found this. In the last decade about 500 CO poisonings and 90 deaths from the back of boats. I will now not only be checking my tanks with your monitor but also the boats themselves.




Dear Mr. Kerr,

It is with great pleasure that I have stumbled on your web site and CO detector from a link on the web site. I am a scuba diver and family physician who is concerned about the air I breath often at up to 5 ATM pressure. The problem with scuba air station fills these days is the monitoring of air quality is poor. Twice a year here in Canada a fill station is obligated by CSA to send an air sample out to an accredited lab. The fill station owner though is not obligated by law to act on a contaminated sample and can continue to fill tanks. He does not have to send his lab reports to any government office I believe unless he has employees who complain to the Ministry of Labor. This is a less than ideal situation.
A recreational diving safety magazine called Alert Diver published an article in 1998 stating that two of the United States  largest air testing labs, Lawrence Factor and TRI, found that between 5 to 8 percent of their air station samples tested over the 10ppm level and several were found to be in the 100 to 200 ppm range. I called one of these labs this week to clarify those figures and was told that samples directly from scuba fill stations greater than 10 ppm are about 3 percent which I still consider far too high. Most of the failures come from fire stations where they might have an older gas compressor or improperly maintained electric compressor. I feel for the fireman that is going to check out a CO alarm and puts on his SCBA unit which has 200 ppm of CO in his breathing air!
The problem in scuba is we breath air under pressures much higher than atmosphere so the partial pressure of CO would be greater at depth and one would want to keep CO contamination to a minimum in scuba air. Many dive shops particularly in places like Latin America and here with the portable compressor use gas compressors where CO can enter the fills.  Even with the electric compressors an improperly placed intake pipe or improperly maintained compressor can lead to CO in the fill.

It is with that background information that I began a search for a product to allow me to check my own fills out in the field before entering the water and decide for myself if my tank is free of CO. In the past there were several scuba dedicated products but these were mainly the gel tubes or colormetric devices and most of these companies have gone out of business.  Recently I was looking at an industrial handheld unit by BW Technologies which costs $375 US and needs to be calibrated often. This is really out of my price range and would not be readily accessible to the recreational diver (single tank, depths less than 130 ft (5ATM)) at this price.

It is with pleasure then I came across your product and would appreciate greatly if you could comment on how I  plan to use your detector.  The best scuba fill would have no CO in the tank but the current standard is to allow up to 10 ppm and the US Navy allows up to 20 ppm. I am interested in a detector which is battery powered, portable, and most importantly quantitative and sensitive in the 0 to 100 ppm range.  Any tank which was found to have more than 20 ppm I would not dive with. An elevated CO is often just a marker for other contaminants like hydrocarbons.

My sampling would be done as follows.  I would put your device in a plastic bag with my scuba mouthpiece in the bag and gently purge air from the tank via the mouthpiece into the bag until the air in the bag is replaced by tank air. I would then remove the mouthpiece and seal the bag. At no time would the device be exposed to any moisture or high pressure air. I would then take a reading on the tank air in the bag. This in fact was how I thought I would use the BWT handheld device and they said that would be fine. Many of the oil and gas workers do this each morning to check their H2S detectors.
There basically is no information on the physiology of CO contamination of breathing CO at depth. The number of deaths attributed to CO poisoning in recreational scuba appears to be very low but some think this may be under reported as many deaths are just reported as ‘drownings’ and the air is not checked for CO unless a suspicion is raised. Not all states and provinces require mandatory testing of tanks in dive accidents or deaths.
In any case I would just like to have a way to lower the risk of CO contamination in my air fills. Let me know what you think about the use of your device in this fashion. You know if it works and is reliable there are something like 3 million recreational divers in the United States not to mention all the technical guys who also need such a device. Could be a large market.

Looking forward to your reply. Are there any Canadian distributors?

Thank you.
Yours truly,
PM., M.D.
Toronto, Canada


Thank You, for your E-mail.
I am Extremely Interested in this Problem that you brought to my attention, which  I was NOT aware of previously.  My Canadian Associate, along with being a Gas Detection Expert, is also a Firefighter, … and a Scuba Diver.
I have forwarded him your E-mail, and I am sure that he will be in Contact with you shortly.

His name is Jim Mackie, and you will find some INFO on Jim on my Website under “Recommended Professionals”.  We WILL work with you on finding the Best Possible Solution to this C O Problem.

Thank You again for bringing this to our attention,
Best Regards,
George E. Kerr, President



Mr. Kerr,

We have been discussing your CO Monitor with folks who are asking about using them on their boats and are concerned about the “High Humidity” issue.

We are not as informed on this issue as we should be. Can you refer me to info in your literature that we already have or address this question for us ?

Thank You


Humidity is a Major Problem for both MOS & ColorMetric sensors; however, … High Humidity is Actually a PLUS for an “Acid Based” Electrochemical Sensor.

My Low Level CO Monitor would be a “NIGHTMARE” on a boat. First, ALL Marine CO Alarms “MUST” have Special “Coated” Circuit Boards to retard the horrible “Corrosive” effects of Sea Air on these Components [Which my Monitor does NOT have] Furthermore, the unusually High Levels of CO that exist when boats are tied up at dockside, would cause my Monitor to be CONSTANTLY in an Alarm Mode.

Unfortunately, UL saw fit to make “DRASTIC” Changes in the “Marine” Version of their UL-2034 CO Alarm Standard, Effective on Oct. 01, 1998, … when they CUT the “ACCEPTABLE” Level of COHb percentage projected at the “Activation” Level, in HALF, from the previous 20%, down to 10%, … the SAME as in the “Residential”   Requirement. This action was a PLUS for the C O Alarm Manufacturers; however, it also Multiplied by MANY Times, the “Nuisance Alarm” Problem for boats at “Dockside”.

I am presently working on a New “Proposed” Set of “Marine” CO Alarm “Activation” Requirements, as a result of an “Inquiry” by the U. S. Coast Guard, for a Review of the “Problems” that are presently being experienced by Boat Owners of all shapes & sizes.

[And, I might add, EVEN MORE SO, by Owners & Rental Companies of Large “Houseboats”, Yachts, etc.

I hope to have some “Unlisted Samples” ready by May, 2003. I will keep you posted.

Thank You, for your questions, and for your Interest in CO Safety,

Best Regards, …………………. George

I am a marine surveyor and yesterday surveyed a 1995 Sea Ray 400 Express Cruiser with a pair of the referenced CO detectors installed. The white plastic face plates of both were discolored due to heat. My infra red meter showed 145ºF on the faces and on the + connection on the back of the one I removed from the bulkhead. The vinyl bulkhead covering was melted where the detector was mounted and the wiring sheath was melted. I have heard of the same problem with the Xintex units mounted on vessels. Both the Xintex and the Rule have been reported to have failed in the same way.

Do you know of any other failures with these or other units. Are these units “marine grade” according to UL code?

I appreciate your thoughts on this.

Alison Mazon, A.M.S.®


Thank You, for your Questions.
I have several things to say in response.
1. If these, or ANY OTHER C O Alarm, were “Installed” in 1995, they should have been REPLACED years ago.
2. These units, like Most C O Detectors / Alarms, made in 1995, utilize a MOS,[Metal Oxide Semi-conductor] type Sensor. Many of these products have experienced internal “Over-Heating” problems, usually due to the use of inferior transformers, and the fact that the MOS type Sensor has an Internal “Heating” coil that raises the internal temperature of the Sensor to in Excess of 482 degrees F, during the “High Heat” Cycle. Figaro “Warns” the Manufacturers NOT to place their Sensor too close to the Transformer, and that the Sensor is Greatly Effected by changes in Temperature and Humidity. Figaro actually offers an IC Chip that does a “Good” job of Temp. & Humidity control; however, due to its “Cost”, virtually NONE of the Manufacturers use it.
[ *NOTE:  Many of the Early Single Station Residential SMOKE Detectors were “Recalled” due to an “Over-Heating” problem that was so Serious that they were Actually STARTING FIRES. Also, I am going to forward you some “Pictures” that show an “Over-Heating” of Recent Models of an Industrial Type Monitor made by IST / AIM.]
3. Your “Term” Marine Grade”, would bring a “Smile” to the faces of many people of the Coast Guard, who are VERY Concerned with the UL “Marine” Standards. In 1995, the UL “Marine” Standard DID have “Different” Activation Levels than the “Residential” Requirements; however, in October, 1998, the C O Alarm Manufacturers convinced UL that for “Cost Savings” and “Ease” of manufacture, these “Levels” should be the SAME. In 1995, the activation level was based of a Maximum COHb effect of 20%. As of Oct. 01, 1998, and Current “Activation” Level is based on a 10% Maximum.     4. Unfortunately, in North America a manufacturer can Continue to SELL a product made to an “OLD” Standard, as long as they can get people to buy it.
5.  Frankly, the HUGE Variations in the Types, Styles, Shapes, Sizes, Construction Designs, etc. in Today’s “Marine” Options, make it VERY Difficult, if not Impossible, to make a “One Size Fits ALL” Standard.
The “Nuisance Alarm” Potential while at “Dockside, or Tied Together in a “Party Cove” grouping, creates a REAL Nightmare for the “Needed” C O Poisoning Protection “Activation Levels”.
6.  Most “Boaters” have NO IDEA of the C O Poisoning Potential that they are exposed to on the waters. If you have not viewed the Marine Section of my Website at: please do so.

As with EVERY “LIFE-SAFETY” Issue that I have had to Deal With in my 50 Years in the Industry, OUR #1 Challenge is EDUCATION, ….. and as John Ruskin said:
“Education does not mean teaching people what they do not know, ….. it means teaching them to BEHAVE, as they DO NOT BEHAVE.”

Best Regards,
George E. Kerr, President
C  O – Experts


Thank you for the very informative response.

The item that rather surprised me is you first statement “they should have been REPLACED years ago”! I really had no idea that age degradation could increase the overheat potential. Periodic replacement is a new concept as far as I know.

And, I had no idea MOS type puts out so much heat. Like too many other surveyors, if we see a working CO detector, we are elated. Just getting them to do that is a major improvement.

I look forward to your photos. I will use them during the education talks I often give and during surveys to stress monitoring condition in addition to function.

Do you have any recommendations on replacement intervals and reasons for said replacement?

Thank you very much for all your assistance.

Alison Mazon, A.M.S.®
Alison,Just another one of my MANY complaints with:
1. The “So-Called” ….. “Life-Safety” Industry.
2. UL

In 1973-74, when we were writing NFPA-74 for Smoke Detection “Requirements”, EVERYONE … KNEW … that a Smoke Detector would not continue to function properly FOREVER; however, the Industry, and the so called “Safety Experts” were afraid that if the Public was told the “Truth”,…that they would NEED to be REPLACED Every 5 to 7 Years,….. that no one would “Buy Them”.
So for the first 20 years, virtually NO ONE talked about the “Replacement Cycle”. Finally, due to the “Growing Number” of Lawsuits, NFPA started a Program to “Encourage” replacement Every Ten Years. Still NOT the “RIGHT” number; but FAR Better than saying NOTHING.

On C O Detectors / Alarms, NFPA initially “Stalled” CPSC for 4 years, before finally starting to write: NFPA 720, Recommended Practices for Installation of Household Carbon Monoxide [CO] Warning Equipment.
Most of this is, as usual, “Based on Manufacturer’s Recommendations”. SO-O-O-o-o, the FOX is still in CHARGE of the HEN HOUSE  ! ! !
The ONLY “GLIMPSE” of “Consumer Protection” is in their statement: “Homeowners should have systems tested by a Qualified Professional “AT LEAST ONCE EVERY THREE YEARS”.
UL and CPSC have done NOTHING on Either: “Time of Manufacture”, … or … “Lifetime” Reliability” … TESTING or REQUIREMENTS.  The New CSA – 6.19-01, … DOES Base their “Lifetime” Reliability Requirements over a Three Year Minimum.

Please take time to Read and Download the “Be Aware” Section off of my Website, and Share it with your Associates. In fact “IF”, you, … or anyone else, that really wants to more fully UNDERSTAND … WHY … we have the Deplorable “LACK of Quality” in our C O Detectors / Alarms, all you have to do is Read Closely the following Sections on my Website, … in this order:
1. The Chicago Story
2 Be Aware
3. C O Standards

When UL “PERMITS” a MAJOR Supplier of C O Alarms continue to Sell a C O Alarm, that States right in the Owners Manual, that under “Ideal” Temp., Humidity, and Air Pressure, … the “Accuracy” of their Display is PLUS 100%, ….. MINUS 40%  … WHAT CAN WE EXPECT  ? ? ?

So-called, “Life-Safety” products that are NOT REQUIRED to be Accurate when NEW, … how in the World can you expect them to Protect you 3 to 5 years later  ?

Frankly, in my opinion that the “PUSH” by CPSC, and others, to “Make Detectors as CHEAP as a DOG’S License”, has created an “Accepted Attitude” of: “ANYTHING is Better than NOTHING”.
I continue to Preach that: “FALSE SECURITY” is WORSE, … than NO FEELING of SECURITY AT ALL  ! ! !

Thanks Again, for your questions and comments,

Very much appreciated information and, sadly, not unexpected. If you look at many of the major players in ABYC you will find industry strongly represented. It takes a long time to get meaningful changes made. And, most changes are compromises. But, it certainly is better than nothing.

I have to publish our western region newsletter this week. Would it be possible to reproduce some information from your website and from your e-mails to me? I would not get into the political realities behind the standards, but stick strictly to the educational aspects.

Thank you for your consideration.

Alison Mazon, A.M.S.®
Alison,You may feel free to print ANYTHING that I write, or “Post” on my Website. Unlike many of the other “Experts”, I DO NOT “Copyright” anything except my “Logo’s”.

Just be sure to Quote me Correctly, and when I say: “In my Opinion”, please so state.
I just Celebrated 50 Years in the Life-Safety Business on April, 13, 2003, and the GREATEST NEED in our Industry is
HONEST Information, … not Mis-Information, …  to promote “Vested Interests”.
I have long said that if you see the Term: “Consensus Standard”, it really means a consensus of what the Industries involved “Agreed” that they can do to Increase THEIR Marketing Success and Profit, …. NOT GREATER Consumer Protection.

I am going to fax you some MOS Data from the Manufacturer of what I believe is the best of the presently available MOS Sensors.
My Opinion: MOS Sensors are acceptable for Combustible Gases, ….. NOT for TOXIC Gases requiring Greater Accuracy, and fewer Cross-Sensitivity and Temp. & Humidity
control problems.

Regards, ……………….. George

Dear Mr. Kerr:

I enjoyed speaking with you on the phone last week.  After our discussion I ordered two units.

I just opened the two CO Experts low level CO Health monitors received from you. (Invoice #002261)

In reading through the literature I notice the caution stating they are not to be installed anywhere that the temperature might exceed 100 degrees Fahrenheit or go below 32 degrees Fahrenheit for more than a 24 hour period.

That raises a concern for me in that I intended to place one of the units in an airplane which lives most of its life on a covered tie-down.  The shade of the cover allows the plane’s interior to closely match the outside ambient air temperature… albeit lagging a little.  Unfortunately in the Phoenix , AZ area that might be 100-115 degrees for as long as 10-12 hours of the day. That plane also occasionally goes to the mountains in the winter for skiing and is exposed to below-freezing temperatures.

Obviously the time above 100 degrees is not a full 24 hours and the time below freezing may or may not be a full 24 hours. However, I wonder if continuous cyclic exposure will shorten the useful life, or alter the accuracy of the unit.

Were I to use this device in a car, I would encounter the same problem.

Please advise me if my concern for frequent cyclic exposures of less than 24 hours is warranted. What detriment occurs to the unit if subjected to those temperature extremes for 24hours or more? Must I (or would I be wise to) remove the unit from the plane when it is parked.

Gratefully yours,

Thank You, for your question, it is one that comes up often from pilots, hunters and campers.

The “normal operating temperatures” listed in the manual are what we consider “normal, ideal, residential temperatures” which produce the very best “accuracy results” from the sensor. As you can see from the following “Link” to the specification sheet from my sensor manufacturer, the “Storage Range” temperatures for the sensor when in an unoccupied environment is a much broader -40 C, to +70 C.

In repeated accuracy tests at colder temperatures down to -20 C we found that the “sensor activity”, thus the percentage of retained accuracy to our original calibration scale, was decreased less than 10%. An “Acid Based” Electrochemical Sensor like the one I use reacts very similar to a car battery, producing a little less “power” when very cold, and also like a car battery, will experience a return to normal performance as the temperature returns to a more normal “lived in” environment room temperature”.

Frankly, I believe that you will find that the temperature extremes will have far more negative effect on the battery “life”, than the sensor “life”.

Please refer your friends and family to my Website for all of their C  O questions.

Best Regards,
George E. Kerr, President / Founder
C  O – Experts

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