Is it necessary to fill your oxygen/Nitrox ready cylinder with Nitrox compatible air when using it for air diving?

When using a cylinder that is designated for enriched air (Nitrox) diving, filling it with standard air is not considered necessary if the cylinder is being used exclusively for air diving. This is because the air we breathe is composed of approximately 21% oxygen and 79% nitrogen, which is identical to the composition of normal air used in recreational diving. In fact, the key concern with using Nitrox tanks is ensuring the mixture is appropriate for the depths and conditions under which you are diving.

However, if divers choose to use a cylinder labeled for Nitrox or enriched air for air diving, it should be noted that the contents and safety protocols related to gas mixtures must be adhered to, in order to maintain the integrity and purpose of the tank. The designation as Nitrox compatible generally refers to the tank's ability to hold higher oxygen levels without risk of complications, not necessarily the requirement to fill it with Nitrox when diving with air.

Therefore, filling a Nitrox-ready cylinder with standard air does not pose a safety or regulatory issue when the intended use is air diving, validating the choice that it is false that it is necessary to fill your oxygen/Nitrox ready cylinder with Nitrox compatible air for such purposes.