little more clarificaiton on TEK plz

I always thought TEK diving was more like underwater welding and breathing fancy gas mixs


Anyone else care to shed some on like TEK diving that really separates it from say just typically cave and wreck diving specialty. Besides well the given of very expensive gear and just going deep.

Also maybe this is a good time to ask...but why not have a course or training for other mixes of gas that don't have to be TEK. I haven't looked into the other gases to really see what they are about or how they effect a persons body.

I thought someone already asked this question a while back but can't seem to find it.

There are various definitions of tech diving, but one common factor seems to be dives where you no longer have direct access to the surface in case of a problem, which then has to be dealt with where you are. The overhead could be a solid, physical barrier, such as the ceiling of a cave or wreck, or it could be virtual, such as a required deco obligation which you can't ignore without a serious risk of injury or death. Either requires more careful consideration of emergency procedures, gear redundancy, gas planning, and being able to keep your wits about you when you can no longer just bolt for the surface.

Ron has pretty much nailed the common definition of "tech" diving -- it's diving where you have lost the option of a direct ascent to the surface, whether that's because of decompression obligation or the presence of a physical overhead. This kind of diving is considered different because of the increased demand for planning, and the necessity to solve problems underwater. The underwater welding, etc., you mentioned is termed "commercial diving".

Also maybe this is a good time to ask...but why not have a course or training for other mixes of gas that don't have to be TEK. I haven't looked into the other gases to really see what they are about or how they effect a persons body.

Click to expand...

I am not sure what you are thinking of here. The commonly used breathing gases are air, Nitrox of various strengths, and helium. Nitrox mixes up to 40% are commonly used in recreational diving, and there are certainly classes for this. Helium's major benefit is reduction of narcosis, so it is generally only used for fairly deep diving, which rapidly becomes "technical", by the "virtual overhead" definition. There ARE classes for recreational use of helium -- such classes are controversial for a number of reasons, including whether helium is SAFE for recreational divers, and whether the high cost of the gas ever justifies its use in the short and relatively shallow dives that would fall under the recreational heading.

Other gases have been tried, but have had sufficient drawbacks (hydrogen, for instance, is explosive, argon is narcotic, and neon is prohibitively expensive) to preclude their regular use for scuba.

thanks guys for the clarification.

I was just wanting more info on heliums benefits and weakness really.

Sometimes for me diving it's not about the depth, its about the time spent down at the targeted depth. Stay at 100 ft for longer then 20 mins.

As Lynn said, the benefit of helium is that it's not narcotic. The main drawback, besides the cost, is that the He molecules are small, and go into and come out of solution quickly. This makes it a more unforgiving gas to use if deco stops are not planned and executed properly.

Helium and nitrogen are both inert gases -- both are absorbed into the blood and tissues, and neither is metabolized, so they both have to be offgassed during ascent. Helium, unlike the extra oxygen in Nitrox, does not do a lot to change no-decompression limits. (It is actually controversial WHAT it does -- some people feel that the decreased solubility means it's better from a decompression standpoint, and others feel that the faster diffusion due to small molecular size is more important. What IS clear is that helium is not friendly to poorly controlled ascent rates.)

If you are looking at trying to get longer dives in the moderately deep recreational range (80 to 100 feet), you are probably better off doing an Advanced Nitrox/Deco class and learning to do some O2 decompression. Helium won't do much for you on those dives.

A simple nitrox course might be a better place to start. It'd add ~50% bottom time in the 80-100' range.

rongoodman:

There are various definitions of tech diving, but one common factor seems to be dives where you no longer have direct access to the surface in case of a problem, which then has to be dealt with where you are. The overhead could be a solid, physical barrier, such as the ceiling of a cave or wreck, or it could be virtual, such as a required deco obligation which you can't ignore without a serious risk of injury or death.

Click to expand...

Well stated.

The_Ghost:

I was just wanting more info on heliums benefits and weakness really. . . . Sometimes for me diving it's not about the depth, its about the time spent down at the targeted depth. Stay at 100 ft for longer then 20 mins.

Click to expand...

There is a recent thread that offers quite a bit of comment which you may find valuable: http://www.scubaboard.com/forums/advanced-scuba-discussions/385336-when-go-trimix.html. With regard to helium and time at depth:

If you stay at 100 ft on 21% (air), according to the (PADI) tables, you have a NDL of 20 minutes.

If you stay at 100 ft 32% nitrox, according to the (PADI) tables, you have a NDL of 30 minutes.

If you stay at 100 ft 36% nitrox, according to the (PADI) tables, you have a NDL of 35 minutes.

HOWEVER:

If you stay at 100 ft for 30 minutes on 21% oxygen (air), you incur a deco obligation of approximately 8 min when using a combination of 50% and 100% O2 for decompression gases (and DPlan as the deco software).

If you stay at 100 ft for 30 minutes on 21% oxygen / 35% helium, you incur a deco obligation of approximately 10 min when using a combination of 50% and 100% O2 for decompression gases (and DPlan as the deco software).

If you stay at 100 ft for 30 minutes on 21% oxygen / 45% helium, you incur a deco obligation of approximately 11 min when using a combination of 50% and 100% O2 for decompression gases (and DPlan as the deco software).

IN CONTRAST:

If you stay at 100 ft for 30 minutes on 21% oxygen (air), you incur a deco obligation of approximately 19 min when using your backgas for decompression (and DPlan as the deco software).

If you stay at 100 ft for 30 minutes on 21% oxygen / 35% helium, you incur a deco obligation of approximately 32 min when using your backgas for decompression (and DPlan as the deco software).

If you stay at 100 ft for 30 minutes on 21% oxygen / 45% helium, you incur a deco obligation of approximately 46 min when using your backgas for decompression (and DPlan as the deco software).

You will get different absolute values, and relative benefit, for different software (and different algorithms) as noted.

ucfdiver:

It's only the ZHL-16b algorithms that have helium taking longer to decompress.

Click to expand...

Therefore, the point of doing this computational exercise is to suggest that the immediate benefits of helium at that particular depth (100 ft) are more likely to be seen in clarity of thinking, and reduced effects of narcosis, not necessarily in times for decompression. As was said, helium may add to your deco schedule with some algorithms, not shorten it. But, you may find alternative value with helium.

Colliam7:

Well stated.With regard to helium:

If you stay at 100 ft for 30 minutes on air, you incur a deco obligation of 8 min when using a combination of 50% and 100% O2 for decompression gases (and DPlan as the deco software).

If you stay at 100 ft for 30 minutes on a mixture of 21% oxygen / 35% helium, you incur a deco obligation of 12 min when using a combination of 50% and 100% O2 for decompression gases (and DPlan as the deco software).

If you stay at 100 ft for 30 minutes on a mixture of 21% oxygen / 45% heliuum, you incur a deco obligation of 14 min when using a combination of 50% and 100% O2 for decompression gases (and DPlan as the deco software).

You might get different absolute values for different soiftware. But, the point of doing this is to suggest that the immediate benefits of helium at that depth are more likely to be seen in clarity of thinking, and reduced effects of narcosis, not in times for decompression. As was said, helium may add to you deco schedule, not shorten it. But, you may find alternative value with helium.

Click to expand...

Actually using VPM+B+2 results in 21/35 having a deco advantage over air, when diving to 150ft for 30min. It's only the ZHL-16b algorithms that have helium taking longer to decompress.

I did my enriched air class, just trying to further my knowledge and see what is going to be my next step in diving.

@collium thnx for the link...good read.

Defintly something I'll have to look into once I get a few more dives under my belt and start wanting to do more complicated dives.