Next step for longer bottom times on deep dives?

[rhwestfall]

I get it, the OP just wants to do this safely:

No hour or more DECO, no crazy depths...

We have some great wrecks here in and around the limits of recreational diving that you just can't get a nice dive on without doing a small bit of DECO. Learning to do it safe makes for some great experiences. I do an annual trip to some fantastic 1800's and early 1900's wrecks that include recreational divers. To watch them fixate on their DC, and race the clock to stay out of DECO is silly....

 

[rhwestfall]

it is a lot more fun than this (buddy was not DECO trained):

 

[flymolo]

Doubles, a stage of bottom gas, a bottle of o2 (or 50%) for decompression gas, and a similarly equipped buddy can get you some pretty long runtimes in the 100-130ft range. no need to add the complexity/risk of a rebreather either.

This sort of dive isn't a starting point after taking something like adv nitrox+deco procedures or tech 1, but it's something to work towards.

 

[wetb4igetinthewater]

I don't understand this, in the context of the OP's question. Can you elaborate?

I was referring to comments like these:

Advanced nitrox/deco procedures. No need for trimix if you're already comfortable on those wrecks. If you plan on going past 130' regularly then mix may be something to consider after a while.

As @Bob DBF has commented: "I was told by one of my mentors, the real problem with narcosis is not knowing you are narked, then finding out during an emergency that you are. That surprise may last long enough to kill you."

 

[100days-a-year]

Meh, OP is already doing these dives just wants a longer BT.
I got mix certified 20 years ago and did some deeper dives on a lot of the deep Keys wrecks and some other East Coast stuff.

Diving mix shallow is a waste of time, money, training and gear for the majority of people doing those dives.
From the Baja California to the Schurz you will see very few divers if ever on mix. Thousands of divers per year if not more do those dives fine on air or nitrox.

Never once saw mix on the Bibb, Duane, Vandenberg, Thunderbolt etc...on up to the <130' NC wrecks. That's probably at least 100 wrecks that get dove recreationally on charters and private vessels regularly. Where are all the deaths and DCS? Should be a regular occurrence but when we hear of them it's normally unhealthy, overweight, inexperienced AND unlucky divers that have isses. Gas choice is rarely if ever mentioned unless its an idiot doing a 300' dive on an Al80 of air.

 

[rjack321]

Never once saw mix on the Bibb, Duane, Vandenberg, Thunderbolt etc...on up to the <130' NC wrecks.

Are the trimix bubbles a different color compared to the air or nitrox bubbles? Asking for a friend, plus wanting to know it when I see it.

 

[wetb4igetinthewater]

Meh, OP is already doing these dives just wants a longer BT.
I got mix certified 20 years ago and did some deeper dives on a lot of the deep Keys wrecks and some other East Coast stuff.

Diving mix shallow is a waste of time, money, training and gear for the majority of people doing those dives.
From the Baja California to the Schurz you will see very few divers if ever on mix. Thousands of divers per year if not more do those dives fine on air or nitrox.

Never once saw mix on the Bibb, Duane, Vandenberg, Thunderbolt etc...on up to the <130' NC wrecks. That's probably at least 100 wrecks that get dove recreationally on charters and private vessels regularly. Where are all the deaths and DCS? Should be a regular occurrence but when we hear of them it's normally unhealthy, overweight, inexperienced AND unlucky divers that have isses. Gas choice is rarely if ever mentioned unless its an idiot doing a 300' dive on an Al80 of air.

This is the normalization of deviance that is so common. One thing I have learned in my own professional training is to respect experts and listen to their recommendations. When it comes to decompression science, I absolutely will follow whatever @Dr Simon Mitchell recommends.

You have been at this game long enough to know that the details of diving deaths is typically not available to the public. Diving deaths are underreported. And quickly forgotten. Many of these are medical. Is gas density a factor on deeper dives? Possible, but again, I'm not qualified to hypothesize. I leave it to the experts who dedicate their careers to dive safety and follow their recommendations based on the peer reviewed research that they conduct.

 

[gamon]

I'm only rec certified, never took a tech class.

I carry an extra 30cf cylinder for reserve purposes and since I let my main tank get lower than most due to having the reserve in the pony I find most often my NDL limits my bottom time not the gas remaining and I tend to always have plenty left at the end of each dive. I don't think I've ever taken a breath off my pony bottle.

So I've been letting myself get into DECO for up to 5 minutes or even a bit more, and do the necessary 10 foot safety stop for a minute or more (whatever the computer advises).

That gives me more time without the time and expense of the tech classes and any additional gear.

 

[macado]

Advanced nitrox/deco procedures. No need for trimix if you're already comfortable on those wrecks. If you plan on going past 130' regularly then mix may be something to consider after a while.

@100days-a-year 's response nailed it.

TDI's Advanced Nitrox/Decompression Procedures (commonly abbreviated AN/DP) is exactly what you're looking for. Other agencies have similar paths to training and may call it different things or allow decompression at different stages with different limits. I just wanted to point out it's a not a unique TDI thing. PADI, IANTD, SSI, GUE all offer similar levels of decompression training. What you're essentially looking for is entry level technical training with some added planned decompression. There are multiple ways to achieve this.

Since you asked about PADI the progression would likely be PADI Tec40 -> PADI Tec45.

From my understanding..
PADI Tec40 limits you to 10 minutes of decompression and one decompression gas up to 50%. Max depth of ~40m/130ft.

PADI Tec45 doesn't have a decompression limit and allows you to use up to 100% (oxygen) for decompression gas. Max depth of ~45m/150ft.

From what I gleaned from their website PADI Tec45 is analogous to TDI Advanced Nitrox/Decompression Procedures.

Once you have decompression training and some experience you simply stop worrying about the no decompression limits (NDLs) clock. It becomes very easy to do ~90-120 minute dives in the 90-130' depth range without too much issue at this certification level with proper planning and training.

I wouldn't really even consider a rebreather or even trimix at this stage although if you're regularly diving to 130'+ with poor visibility/strong current introducing some helium may not be a bad idea. GUE Tech 1, TDI Helitrox allow helium at that level but that's maybe an entirely different topic. I'll leave others to argue this point.

 

[rddvet]

Gotta love when people say trimix is pointless cause they never get narked. Or you're just narked and don't notice it. I've seen plenty of people dive trimix on the wrecks 100divesayear brought up. Agree that it's a normalization of deviance, with either a little chest thumping or cluelessness mixed in for the people that are so adamantly against trimix at depths just past 100ft.