Scuba Tank Fill Stations and Carbon Monoxide Analyzers (2024 update)

Carbon monoxide (CO) is an odorless, tasteless, and invisible poisonous gas that has claimed the lives of scuba divers worldwide when present in their air tanks. CO can enter scuba cylinders when exhaust gas is drawn into the compressed air intake. Gas detection is crucial for divers, as the effects of carbon monoxide are amplified at depth. To protect themselves from potentially lethal CO exposure, divers should use a low-level and sensitive carbon monoxide analyzer designed specifically for scuba diving. These analyzers continuously monitor the air in the tanks, alerting divers to the presence of CO and preventing tragic accidents.

Pros	Cons
A Carbon Monoxide Analyzer for Scuba is the only way to confirm if your tank is not contaminated with carbon monoxide gas. CO Analyzers save lives and can prevent a diving catastrophe. CO Meters for scuba have become more affordable and cost less than $300.	Do not use a CO home alarm, they alarm over 70ppm, that is too high for a dive alarm. Divers should choose carbon monoxide detectors carefully to ensure the right sensitivity. Always check your air tank for zero ppm levels. Exhaust gas can enter the air compressor and end up in your tank.

Best Carbon Monoxide Detector for Scuba?

For maximum safety, we believe the best scuba CO detector should:

• have a resolution of 0.1ppm (to detect the smallest CO concentration)
• be waterproof for rugged outdoor / or on-boat operation
• be drop-proof (only a matter of time before it drops, especially on a boat)
• be battery operated and last for over 1 year on a single battery
• one button operation for easy novice use

Forensics Detectors Low Level CO Detector (0.1ppm resolution)

 

Sensorcon Waterproof Carbon Monoxide Detector

DE-OX SAFE Carbon Monoxide Analyzer

Pocket Carbon Monoxide Detector

Pro CO Alarm Analyzer

Analytical Instrument Palm CO Analyzer

DIVENAV COOTWO (discontinued, company does not exist)

How does Carbon Monoxide Enter a Scuba Tank?

A scuba tank gets contaminated with CO when CO either finds its way into the compressor intake of the compressor filling station, or when the compressor overheats and burns the lubricating oil, and is then compressed into the scuba cylinder. Sources of carbon monoxide gas include:

• CO may come from the compressor itself, as they are often powered using a gasoline engine.
• CO may come from an adjacent source such as a portable generator, RV exhaust, boat exhaust or another gas-powered scuba compressor.
• CO gas may come from lubricating oil in cylinders leaking and burning due to friction, or a poorly maintained compressor overheating.

What Carbon Monoxide ppm Level is Dangerous to Divers?

• In our opinion zero ppm of CO in a cylinder is best. Zero ppm should be the expected CO concentration of any dive scuba cylinder and any amount above this, while perhaps still safe, indicates that there is CO in the atmosphere which is not an acceptable situation.
  
  
• Allowable CO concentrations varies depending on the applicable authority, and ranges from 3ppm to 10ppm. Scuba cylinder CO standards is include  EN 12021 (Europe), CZ275.2 (Canada), SANS 10019 (South Africa) and CGA Grade E (USA), AS/NZ 2299.1 (Australia).
  
  
• As we dive deeper, the partial pressure of carbon monoxide will rise, increasing the actual number of molecules per breath, therefore the degree of "poisoning" and CO exposure is also a function of dive depth and time (see below DAN table 2 - thanks to Francois Burman for allowing us to present the table).
  

Why is Carbon Monoxide Dangerous to Divers?

CO gas is a toxic substance that induces fatigue, headaches and drowsiness at best. 

CO is very dangerous during diving because it has a strong affinity for hemoglobin, which serves as the body's main oxygen transporter. Hemoglobin is at least 200 times more prone to binding to a CO molecule, which converts some of it into carboxyhemoglobin (COHb).

This means that less hemoglobin is available to deliver oxygen to the tissues to the diver. The amount of COHb increases, rapidly depriving tissues of oxygen which create a suffocation scenario.

When the oxygen levels in our tissues fall too low, and the bigger the amount of CO molecules, the higher the percentage of hemoglobin that converts to COHb (percent COHb) and the greater the injury. 

Scuba Fill Station Locations

Most fill station keep their compressors indoors to prevent tampering and reduce exposure to the elements. This means they require two important things. First they require excellent ventilation to the room to provide the fill air. And the second is an exhaust port that is not compromised and runs to the the outdoors to evacuate the combustion exhaust.

Many times, the exhaust comes back into the fill room via leaks in the exhaust vent pipe. 

Below are some photos of a fill station in Fiji that I took on my vacation. As you can see, a compressor is located in an isolated room.

The scuba technician fills the tanks in the room from the fill compressor, then gives the tanks to the customers in the training dive pool and to customers going scuba diving at the nearby Fiji reefs.

What Should You Do When the Carbon Monoxide Meter Detects Carbon Monoxide?

If your CO meter detects carbon monoxide in your scuba cylinder, do not use the cylinder. Consider the following:

• Test any additional cylinders provided by the same dive shop
• Call the dive shop and alert them of the CO contamination
• Return the cylinders to the dive shop

Shall I use a Home CO Alarm to Check my Tank?

No. Do not do that.

Even if the CO alarm has a ppm digital display, most units display a minimum of 30ppm. Units that dont have a display, alarm at 70ppm following the UL2034 protocol. 

In other words, home CO alarms will not give you the sufficient early warning alarming and CO concentration information to undertake a safe and effective analysis of your scuba tank. Dont do it!

Have Divers Died from Carbon Monoxide Poisoning?

Yes.

Deaths and injuries from CO in scuba tanks has been a problem for many years. These stories can be found in the news. Some examples include:

• More recently in 2022, after the death of a diver in Queenscliff, Australia, inspectors found three cylinders at the site contained carbon monoxide levels of at least 150 parts per million (PPM) – more than 30 times the maximum acceptable carbon monoxide level of 5 PPM. 
• The story of a military diver who experienced serious poisoning brought on by hydrocarbons in his air. The hydrocarbons were produced by a broken compressor that was used to fill the diving cylinders and sucked in the motor exhaust. Hypoxia and hypercapnia added to the already existing symptoms of exhaust gas poisoning. Consciousness was lost. The diver was brought to the surface and supplied with oxygen. 
• Ten boys who were taking a dive class in an indoor pool in England were involved in an incident that was described by McDermott et al. in 2018. Six people showed signs of CO poisoning and had COHb levels ranging from 6.2 to 32.8 percent. The youngster who was afflicted the most briefly lost consciousness, had pulmonary edema, elevated troponin, and had diffuse white matter hypodensity and cerebral edema on a head CT scan. With the help of normobaric oxygen therapy, every affected boy fully recovered. Eight out of 15 air tanks gathered from the area around the pool showed levels of CO greater than 1,000 ppm. Gas samples from the high-pressure bank at the diving shop where the cylinders were purchased revealed 2,550 ppm CO due to a malfunctioning compressor. 

Who Needs a CO Detector for Scuba?

• Scuba stores and operators
• Cylinder fill station operators
• Scuba and Diving Expedition operators
• Scuba Instructors and Trainers
• Firefighters using self-contained compressed air breathing apparatus
• Scuba divers
• Commercial divers
• Military divers
• Air divers
• Trimix diver

Can I Trust my Scuba Cylinder Fill Station?

Yes and No.

If you are traveling to new places, maybe a new country, just be aware that scuba fill stations may not require to be maintained as strict as those in developed countries. In these cases, ensure you have your own CO detector to check your scuba air.

FireFighters and their self contained compressed air breathing apparatus?

There are instances that firefighters compressed air is also contaminated with carbon monoxide. So in other words, the dangers that exist for scuba and divers, are also a problem for firefighters using compressed air apparatus.

How Expensive Are Carbon Monoxide Detectors?

CO detectors range in price, however for testing scuba cylinders, a very sensitive 0.1ppm resolution CO detector is recommended. These units are more expensive than your typical carbon monoxide home alarm.

How Long Do Carbon Monoxide Detectors Last?

The average carbon monoxide detector lasts between two to three years. Home CO alarms last up to 10 years, however CO meters and CO detectors made for scuba cylinder testing, last from 2 to 3 years.  

What Gases Does a Carbon Monoxide Detector Detect?

Carbon monoxide detectors are made to solely pick up carbon monoxide gas. CO sensors made from electrochemical technology do have some sensitive to high humidity and hydrogen gas. However, in a typical dive scenario, these cross-sensitivities will have minimal impact. 

Just be aware, that if you are testing in a very humid location, make sure to ZERO calibrate your CO detector first to remove any lower baseline drift.

Can I Use a Carbon Monoxide Detector Myself?

Yes.

Anyone can use a carbon monoxide detector to test their scuba tank. Some scuba stores will even test your cylinder for free.

Do I Need a Digital Display for My Carbon Monoxide Monitor?

For scuba testing, it is best to use a super sensitive low level carbon monoxide digital detector which a digital ppm display to see exactly the CO concentration. This will assure you of low level sensitivity to detect the smallest amount of carbon monoxide that may have been compressed in your tank.

How Do I Test my Carbon Monoxide Detector?

It is best practice to periodically bump test and calibrate your carbon monoxide detector to assure accuracy and confidence in operation.

Final Words

Scuba divers must prioritize safety by using a CO monitor or ensuring their fill station operator confirms zero ppm of CO in their tanks. Carbon monoxide monitors, also known as alarms, meters, or detectors, are essential for preventing CO contamination in scuba cylinders, which can lead to dangerous levels of the gas. Although different allowed levels of CO in cylinders range from 3 to 10 ppm, divers should strive for ZERO ppm to minimize risks. Proper gas detection involves regularly testing and calibrating CO detectors to ensure they operate correctly, providing accurate readings and timely warnings to keep divers safe.

About the Author

Dr. Kos Galatsis ("Dr.Koz") is the President of FORENSICS DETECTORS, where the company operates from the scenic Palos Verdes Peninsula in Los Angeles, California. He is a subject matter expert on gas sensor technology, gas detectors, gas meters, and gas analyzers. He has been designing, building, manufacturing and testing toxic gas detection systems for over 20 years.