Can open circuit technical divers go down to 400+ feet or is a CCR Rebreather required?

[Doby45]

 

[IDS_Bill]

For me, they main drag about diving that deep on OC is the increased deco time (twice as long in some cases). You still have to carry the same amount of deco gas/bottles to cover a rebreather failure at depth but the hang time is rough on OC. 10min at 342 ft got us 1hr deco time. Luckily it was on the drift in Playa del Carmen so it was a wonderful hang.

 

[Subcooled]

I do not know much about rebreathers, but I do know that at 300 feet any breathing gas is about 11 times as dense as it is on the surface (add 1 atmosphere for each 30ft). This applies both to open circuit gas and to recycled gas in a rebreather. A rebreather has a carbon dioxide filter, a box of sofnolime, though, that one has to breathe through. A "sandbox" really doesn't make breathing easier. It should be easier to breathe from an open circuit system at great depth. A rebreather both removes old and creates new risks. Whichever is better for a specific task at those depths I cannot tell due to no experience.

 

[Macan]

Yes, you can do a 122m (400 ft) dive on OC. This is with Trimix at 10:66 (10% O2 and 66% He) at 1.3 PO2 to give you an EAD of 30m. OC is commonly used for this.

Using a CCR has advantages and disadvantages. One of the biggest advantage of a CCR is optimized decompression. On a CCR, you can set your inspired PO2 to be constant at 1.3 throughout the dive. On an OC, PO2 will drop as you ascend then rise and drop again when you do a gas switch for your deco obligations and continue your ascent.

 

[The Chairman]

but when we do the big dives the yellow boxes stay topside.

That's an indictment against those yellow boxes. It's why I chose an SF2, though I doubt I'll ever do 400.

 

[Remy B.]

Can open circuit technical divers go down to 400+ feet or is a CCR Rebreather required?

 

[Remy B.]

I don't know if Khalil still in the Board and reading, but I will speak from my inexperience perspective, you are asking questions way ahead and in the diver experience, it kind of reminded my self when I started in the Board and I was new to diving ( Still are ) except that my questions where down to 150' feet, no rebreather, no exotic gases, because with the little training gained I knew everything beyond 150' is a dead trap for recreational divers, you are asking big questions that even with the grace and patients that the experience guys are explaining and from which you will have good answers, it just will be a tip of the iceberg, there is so much more involve in to complement and understand that you have no idea.

it cross my mind that you are very new to diving and are very enthusiastic and maybe you hear from your dive instructor that you did well during your OW course, and that it went very easy, and you are thinking this es a piece of cake, for OW it really is, for the questions you are asking they are far from easy, /// Or that you are hearing stories from other divers that may think they have it under control and they actually are misleading you,/// Or you know about something of value that is laying around 300 and 400 feet , to drive you to ask those questions you posted.

Like I said I'm a rookie, but now you have heard it from both sides of the diving community, forget rebreather, 150'+ Feet depth questions, it gets complicated, very expensive and dangerous as well, I'm a week from completing my AN/DP + Helitrox courses all three together, and it is not easy, and not cheap and there is still a lot to learn, practice and spend money on, and that is just to stay in the 140' feet range with small Deco's