Gas Analysis - Keeping yourself safe while cave diving!

Recently I read a harrowing article about two divers who almost died and are suffering long term debilitating effects from breathing what we generally refer to as “Bad Gas”. The impetus of this article is to help readers know what “Bad Gas” is and some tips as to how to avoid getting & breathing “Bad Gas”.

To see test results from our compressors click HERE.

Florida law requires any vendor of breathing gas to have it tested on a quarterly basis at a minimum. Industry standards require vendors have it tested anytime they suspect that some event has made the potential for them to be pumping “Bad Gas”. The vendor should post the gas analysis certificate in a conspicuous place for customers to view. Some vendors only post the certificate, some post the actual test results similar to what is shown below. Clearly you should make sure you see these certificates and read them. While it is no guarantee the gas is good, it is a good start.

What is “Bad Gas”? There are standards for purification that determine whether or not a gas sample meets minimum standards for purity. There are several things that are checked in order to help make this determination. Some of the more obvious ones are: Carbon Dioxide, nitrogen, oxygen, argon, carbon monoxide, water vapor,  hydrocarbons, methane, and oil.

Some of the things you can also do is to take a look at the compressors where you get your gas fills. If they are dirty that should tell you something. Dirty compressors do not cool as well as clean compressors. The very fact that a compressor is dirty tells me volumes about the staff at the facility. Consider the ventilation around the compressor. Compressors need to be cooled – many operators blow air across the compressor while it is running.

If the air temperature around the compressor is hot it can render the Hopcalite in the filter to be ineffective. Hopcalite is a catalyst that coverts carbon monoxide to carbon dioxide. If the Hopcalite gets much above 100 degrees Fahrenheit it will no longer convert CO to CO2. Hopcalite is advertised to handle as high as 300 ppmv of CO. If the oil reaches its flashpoint the Hopcalite will be unable to handle & convert that volume of CO to CO2 so you will get a lot of CO in the breathing gas.

If the gas coming through the filter is moist it will also render the Hopcalite ineffective. The dew point must be at least -50 degrees Fahrenheit. Because of this there must be a drying agent in the filter before the gas reaches the Hopcalite in the filter.  You can note that the CO in the reported sample is less than 0.3 ppmv. The filter in this compressor has a Hopcalite layer in it.

Compressor operators are wise to run their compressors when it is cool and dry, if at all possible. Running the compressor at the hottest and most humid part of the day may be required to meet gas volume demands. If the compressor is being run during these times extra care should be given to cooling the compressor and ensuring adequate ventilation.

Compressor operators should be using synthetic oil rather than mineral oil. Synthetic oils have a higher flashpoint, are not as bad for you if breathed. (But it is still not good). Ask your vendor what they use; you may be surprised at some of the responses.

Operators would also be wise to install CO monitors in their gas system. CO monitors are available for purchase at retail for $400. This seems to me a small price to pay for the vendor to constantly monitor for CO. These are also relatively simple to install. Ask your vendor if they have a CO monitor.

After you get your tanks filled and before you connect your regulator to your tanks crack open the valve and perform a ‘sniff test”. While this test is not all encompassing it may yield a result that will tell you NOT to dive that gas. If the gas has any odor to it at all, do not breathe it. Tell the supplier of that gas that it has an odor and give them the opportunity to correct any problem that may exist. Some people I know have sent samples of these bad smelling gasses out for analysis.