Scuba cylinders in oxygen-enriched and oxygen service –
Posted by Luxfer

"It’s really important that I have enough pure oxygen in my decompression cylinder, when I need to use it after a deep dive."

Is it okay to put extra oxygen in my cylinder to make sure that I don’t run out?

DOT regulations (see CFR 49) strictly prohibit over-pressurising a scuba cylinder containing any kind of gas, but it is particularly dangerous to do so with high oxygen concentrations. The reason is: The higher the pressure and the higher the oxygen concentration, the higher the risk of a fire and explosion if a contaminant is present.

Luxfer has received numerous and persistent reports that technicians in certain sectors of the recreational diving community routinely over-pressurise scuba cylinders, including cylinders containing high concentrations of oxygen.

This is sometimes described as “doing divers a favour,” offering “a little more down time” or “giving divers their money’s worth.”

Not only is this an unsafe practice, it is against the law!
Under no circumstances should you allow the gas pressure in your scuba cylinder to exceed the service pressure for which the cylinder is designed and stamped or marked.

If a filler offers to over-pressurise your cylinder, you should not only refuse the offer, you should report the filler to the DOT. If you suspect that your cylinder has been over-pressurised, you should have it depressurised and have it inspected by a competent technician to determine whether it is fit for further service.

For pure oxygen, DOT mandates strict pressure limits:

Gas pressure in an aluminium cylinder containing pure oxygen must never exceed 207 Bar even if the cylinder is stamped for a pressure above.

If you are concerned about running out of oxygen, use a larger decompression cylinder filled to the proper service pressure—or carry more cylinders.

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Oxygen Compatibility in Catalina SCUBA Cylinders

PLEASE NOTE: This document only applies to Catalina Cylinders, new and used, SCUBA cylinders and in no way is meant to apply to the SCUBA cylinders manufactured by different entities.

Prior to June 2006, Catalina Cylinders SCUBA cylinders, as-manufactured, were not specifically cleaned for oxygen service and therefore are under no circumstances to be charged with oxygen enriched air, air containing oxygen concentrations in excess of 23.5%, unless the SCUBA cylinders have been specifically cleaned for oxygen service by trained personnel and labeled as such.

As of June 2006 all 3000psi service pressure, or less, Catalina Cylinders SCUBA cylinders, as-manufactured, have been specifically cleaned for oxygen service and therefore can be charged with oxygen enriched air immediately after purchase.

To charge a Catalina Cylinders SCUBA cylinder with oxygen enriched air, the following items must be verified before charging:

The cylinder is currently clean as if for oxygen service. It should be a new 3000psi or less Catalina Cylinders SCUBA cylinder or a used Catalina Cylinders SCUBA cylinder that has a cleaned for oxygen service and a label affixed stating as such.
All accessories and components which will come in contact with the oxygen enriched air charge have been manufactured cleaned for oxygen service or have been cleaned and certified as clean for oxygen service by properly trained personnel.
All lubricants used on Catalina Cylinders SCUBA cylinders, all accessories and components which come in contact with the oxygen enriched air charge are compatible with high pressure oxygen usage and aluminum.
The o-rings and other non-metallic materials which come in contact with the oxygen enriched air charge are compatible with high pressure oxygen usage.
All other items and materials that may come in contact with oxygen enriched air during the charging, use and/or storage of the Catalina Cylinders SCUBA cylinder and its components and accessories which have been cleaned for oxygen service, have been cleaned for oxygen service.

Warnings

Failure to verify the above items have been addressed before charging a SCUBA cylinder with oxygen enriched air may lead to a catastrophic event that can cause property damage, serious injury or even death.

The U.S DOT has interpreted its regulations stating that DOT-3AL (aluminum) SCUBA cannot be charged with oxygen enriched air to a service pressure greater than 3000psi (207 Bar).  Thus, Catalina Cylinders 3300psi (227 Bar). compact SCUBA cylinders cannot be charged with oxygen enriched air as mandated by the DOT.

For more information on this matter please contact Catalina Cylinders.