​Proper decompression bottle marking is critical to safe technical diving.  Switching to the wrong decompression gas is unacceptable and CAN KILL YOU.  To reduce the risk of the diver breathing the wrong decompression gas, the deco bottle must:

  • Be clearly marked and easy to read - no unnecessary information
  • Have the deco gas' MOD clearly marked on both sides of the bottle
  • ​Have the analysis tape on the shoulder of the tank, including; mix, date analyzed, pressure and initials of the analyzer

Analysis tape is placed on the shoulder of the bottle and contains the bottle’s mix, MOD, date analyzed, bottle pressure and the initials of the analyzer. No additional information is required or needed on the main body of the bottle.

If you wish to have your initials on your bottle, they can be placed on the on the bottom of the bottle, in such a way to not interfere with the MOD markings or cause confusion, as illustrated in the picture to the upper right.

Other Markings
To keep the sides of the bottle clean, the visual inspection sticker is placed on the foot of the tank.  The visual inspection sticker serves no purpose to the operation of the dive or the gas switch, so it therefore not needed on the body of the tank. 

No other markings or stickers are to be placed on the bottle.  To do so could cause unnecessary distraction or confusion during the critical gas switch procedure.

For bottle rigging instructions, see the
Bottle Rigging Page


Marking the Bottle - MOD

During the gas switch process, the diver and his team will reference the MOD sticker on the sides of the bottle. 

Since the primary risk the diver has during a gas switch is switching to the wrong gas, resulting in oxygen toxicity, the only marking on the sides of the bottle is the MOD of the gas in that bottle (1.6 PO2 for deco bottles).  

For bottles containing EAN50, the bottle would simply have “70”, for 70fsw, on each side of the bottle.  A deco bottle containing 35/25 will simply have “120”, for 120fsw, oriented to the person reading it.  The “inside” sticker of the bottle, which the diver will be verifying against, will be oriented to the diver.  The “outside” sticker of the bottle, which the team will be verifying, will be oriented to the team. 

​The only exception to the above method of labeling decompression bottles is for bottles containing 100% oxygen.  Since the MOD for oxygen is 20fsw, and “20” can look very similar to “70”, if the diver were to mistakenly switch to oxygen at 70fsw, running a 3.1 PO2, the results would most likely be tragic.  Therefore, the oxygen decompression bottle is labeled “OXYGEN 20”, illustrated in the picture to the right.