I'm a certified Tech Diver if anyone has questions (TDI AN/DP & Heliox). Fun fact is the narcotic effect is very sudden for most people at a certain depth (30m

I'm a certified Tech Diver if anyone has questions (TDI AN/DP & Heliox). Fun fact is the narcotic effect is very sudden for most people at a certain depth (30m for me) and also clears just as quickly. It's more pronounced if you are tired and/or the water is cold. Helium is very expensive like you say. Normal air fills are like $10 AUD, a tank of Trimix can be hundreds. https://www.scubadoctor.com.au/trimix-requested-mix.htm https://www.scubadoctor.com.au/trimix-requested-mix.htm. Normally you would need 3 or more 12L tanks filled with 240L of gas in each, depending on the dive. Most people who use it a lot do rebreather diving, where you can recycle a few liters over and over. The rebreather costs $10k AUD + training though and has many more parts that can fail. One is the oxygen sensor, that has limited lifespan and if it fails and you don't catch it quick enough can kill you (you switch over to bailout which is a backup gas supply).