When making decompression dives we need to ensure we have gas available to complete our required decompression stops. More commonly than not we use different gasses, with a higher percentage of Oxygen to “accelerate” our deco.
When selecting our deco gasses we have to take a few things into consideration. We need to keep our oxygen partial pressure at between 1.4 and 1.6 to really get the benefits and speed our decompression stops. Therefore if we have many stops at different depths it is a good idea to carry more than one deco gas. When we are planning a dive as a team it is important that we all plan our gasses together and everyone uses the same gasses. This reduces confusion while gas blending, and also helps keep the team together while completing deco stops. (As opposed to one person gas switching on to 80% at 9m and one person switching on pure oxygen at 6m). So if there are any problems your team mates can help out.
At Davy Jones Tech we use a set of standard gasses while diving, to make dive planning easier and to ensure if we overstay our time we can have contingencies already written out in our wetnotes. As you progress through the tec courses not only will you progressively go deeper, you will also start increasing the oxygen concentration and eventually the amount of deco gasses you will carry.