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Gas regulators and Fittings

Posted by on Thursday, May 24, 2018 in Uncategorized.

Since 1913, the Compressed Gas Association has been dedicated to the development and promotion of safety standards and safe practices in the industrial gas industry. More than 110 member companies worldwide work together through the committee system to create technical specifications, safety standards, and training and educational materials; to cooperate with governmental agencies in formulating responsible regulations and standards; and to promote compliance with these regulations and standards in the workplace. (From the CGA website:

The most frequent compressed gases used in basic science research are CO2, Nitrogen, and Compressed Air. However, the regulators and fittings required to attach to these tank are not interchangeable. The CGA has purposely required these differences to prevent potentially dangerous situations where personnel incorrectly use hardware. Some gases are more corrosive than others which require different internal components. For example, dry CO2 by itself is not corrosive. However, if any moisture gets into the regulator, the result can be the formation of carbonic acid. Some gases require a regulator with a higher "pound burst" rating than others. To help identify what fittings and regulators go with what types of gases, they have outlined a specific nomenclature to help:

CGA 320 – CO2 (2000 lb burst fittings)

CGA 540 – O2 (3000 lb burst fittings)

CGA 580 – Nitrogen, Argon, & Helium (3000 lb burst fittings)

CGA 590 – Compressed Air and *Compressed Air/CO2 mixtures (3000 lb burst fittings)

*Note: You cannot use a CO2 regulator if you have a 10% or 20% CO2 tank mixed with air.


There are reports of adaptors being sold on the web which would allow one to attach, for example, a Nitrogen regulator to a CO2 tank, circumventing the CGA's safety precautions. Beyond the obvious concerns, other issues can arise. Flowing 100% CO2 through a nitrogen regulator can cause it to freeze up due to design differences in the various regulators. The temperature of CO2 is dependent upon its vapor pressure.The freezing up can cause damage to the diaphram. Here is an explanation from a recent blog:

"There is liquid CO2 in bottom of CO2 cylinder with gas above the liquid until cylinder pressure is below CO2 vapor pressure which varies depending on temperature. When CO2 in cylinder is below vapor pressure all the CO2 in cylinder is gas.

When you start flowing withdrawing gas, from above liquid in bottom of cylinder, a CO2 fog will form above the liquid and flow out with the CO2 gas. In air conditioning this fog is called latent heat because the small liquid CO2 particles needs to absorb heat to change to CO2 gas. This heat will be absorbed readily from metal cylinder walls, metal of regulator, metal or rubber regulator diaphragm causing anything else it touches to get cold quickly. A low flow CO2 regulator for a beer keg will not have problem freezing. A higher flow rated CO2 regulator might have built in heat exchanging fins to help prevent freezing. For even higher and or prolong flow rates the regulator would have electric heater to prevent freezing."


While adaptors may work for a period of time, it is always best to error on the side of caution and obtain the correct hardware than to take a shortcut with potential hazards. After all, the safety of our lab personnel should be the most important consideration in this matter. For assistance with any technical questions related to regulators and fittings, please contact your supplier or the Equipment Manager for help.


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