Oxygen is mainly used to speed the shallow decompression stops at the end of the dive. It is only safe down to a depth of 6 meters (maximum operating depth) to avoid oxygen toxicity. The cylinders we have are prepare and clean for oxygen service. Also the o rings and lubricants we use on them. Actually we can fill your oxygen tanks up to 200 bars /3000 psi with our booster. Also we recomend seriously to analize and label the tanks before use them.