The terms “formal oxygen cleaning” and “informal oxygen cleaning,” which appear in some non-Luxfer scuba manuals, are intended to differentiate between formal, government-mandated oxygen-cleanliness documentation required in the gas and medical industries, as opposed to less-formal documentation used in the recreational diving industry.
Unfortunately, some scuba technicians and divers have erroneously interpreted “informal cleaning” to mean that a less-rigorous, less-thorough level of oxygen cleaning is required for scuba equipment—even though the scuba manuals that use these terms make it quite clear that the same careful cleaning procedures and acceptable cleanliness levels should be used with all equipment in oxygen service. Moreover, the term “informal” is often associated with the so-called “40% rule,” from which some divers and technicians have wrongly inferred that the recreational diving industry somehow has special dispensation to clean cylinders to a less-stringent standard and at a higher oxygen-content threshold than other industries (see Question 4, above).
Because of these erroneous and potentially dangerous misinterpretations, Luxfer chooses not to use the terms “formal” and “informal” when referring to oxygen cleanliness. Oxygen clean is oxygen clean—there are not different levels of cleanliness.
As for documentation, it is always a good idea to thoroughly document all aspects of your oxygen-cleaning procedures and maintenance. Such careful record-keeping can be very valuable if an oxygen-related incident occurs.