SDTechDiving

RANDOM PHOTOS

If divers have not been experiencing this, its most likely that they haven’t got much argon in their suit anyway! Remember that the Cold just hurts, it doesn’t kill. Getting cold does not worsen your chances during decompression, before you pull huge deco’s, practice the same time period to see how cold you will feel at the end. Back gas or nitrox mix up to 40% or air is a better alternative to argon. Also this avoids the ridiculous argon bottle (often filled with air :-)

With regard to the construction of dry suits…consider the following, where will you be spending most of the dive? Probably doing decompression…If this is not the case…it doesn’t matter what suit you wear! If you do complete long decompressions…6-8mm Neoprene will keep you warmest for longest. Compressed neoprene or tri laminates are lighter and “possibly” more comfortable on the surface, but these types of material have virtually no insulating properties and rely heavily on under suit selection. You will not get any heavier at maximum depth with a neoprene suit compared with a membrane suit. If you can dive a membrane or crushed neoprene without an under suit, you probably don’t need the drysuit in the first place. Undersuits at depth definitely compress as much as thick neoprene! Drysuits make very poor back up buoyancy alternatives, unless you are wearing the lightest of tanks in warm water. Consider a dual bladder wing.

If you can, wear a wetsuit. This fixes the urination/hydration issue also ;-)

For dives shallower than 60m for no longer than 20minutes…then any training manual, and, virtually any decompression program will give you a fairly reliable ascent plan.

For deeper dives: Keep the Helium as low as experience allows, When choosing decompression gases, when you make a raise in oxygen, drop the helium by this amount. You must keep the nitrogen % constant or dropping. Keep helium in the decompression gas right up to the oxygen stop at 3-4m. By keeping your decompression Po2 less than 1.4 you will avoid making po2 breaks (air breaks.)

Air breaks, while decompressing on oxygen, from a Trimix dive may cause type 1 bends later, due to counter diffusion (on extreme dives). Counter diffusion will cause far worse bends during a deep decompression stop (type 3 and 2) if the decompression gas contains insufficient helium and the ascent ceiling is violated or near.

Decompression Table Design

Decompression table designers used to work for large, often government backed organisations and institutions. Names that deepened the well of decompression understanding are well known and respected. Haldane, Workman , Buehlman and the many others that have furthered our understanding spent many years analysing decompression data taken from men working in hyperbaric environments both dry and wet, and then refining the results to reflect what needed improving. Much of the research into decompression theory has been driven by the oil industry and commercial diving companies. Additionally many navies around the world have seen the tactical benefits in understanding the inter action between man and the undersea environment. These two large research entities have made big leaps with the knowledge to descend a person deep underwater and return them safely and undamaged.

Since the drive for oil production has largely turned to remote and robotic means, and the navies have realised that the risk/reward equation is unbalanced when sending human beings without protection against the massive pressures found underwater, the need for refined decompression data has dried up. Divers could be reasonably assured by the research conducted in the past, and the fact that the tables were validated during actual experiments on men and woman.

The dive profiles that technical divers call routine are quite unlike the controlled dives that commercial and military divers repeat everyday. Decompression theory is advancing at a much slower speed than the desire to descend deeper and longer by technical and recreational divers. In the last 10 years a new breed of decompression “experts” are emerging, they offer untried and un tested methods that are propagated through the internet to a hungry audience.

Some of the new decompression techniques are based around traditional decompression algorithms that, with a few modifications can be reliable when used conservatively. Other table designers have ventured completely away from historically validated methods and have marketed radical decompression algorithms that received no verification through human testing. Unfortunately the designers of decompression software are very happy to let their customer base be the testers of the product.

Decompression injuries can occur instantly or manifest themselves over years. Divers wishing to dive outside traditional methods of decompression should take time to understand the implications, and attempt to analyse the ascent plan using knowledge from truly experienced divers or software products designed to compare past human based test data with newer math based alternatives. The decompression analyser ”DecoChek” developed by Stephen Burton is an excellent tool for divers to obtain decompression plan comparisons and analysis data.

There are many versions of dive software on the market. Models based on dissolved gas theories have many verification dives. The models based on free gas elimination, have been tested in various net experts imaginations only. Free gas models will slowly merge with traditional models over time, as the their bends incidence increases. Free gas models are associated with very deep stops that actually increase decompression loading later, that they don't compensate for. They have been poorly validated mainly during moderate dives to 90m. While you might not get bent using them everytime, your bones and circulation will suffer in the long term. This is the reason that the developing scientists discontinued work on these models in the late 1970’s! The IT specialists that have reincarnated them recently, are interested in your cash now, not your arthritis later…you have been warned ;-)

Page 2 of 3

PREVIOUS PAGE

This article was contributed by Mark Ellyatt, owner of Inspired-Training.com and author of the book Ocean Gladiator and can be contacted through his website or by email. The articles presented here do not necessarily reflect the beliefs and/or opinions of SDTechDiving; they are the sole written opinion/expression of the authors. SDTechDiving is not responsible for content contained within this article, including links which may take the reader to websites outside of our control.

If divers have not been experiencing this, its most likely that they haven’t got much argon in their suit anyway! Remember that the Cold just hurts, it doesn’t kill. Getting cold does not worsen your chances during decompression, before you pull huge deco’s, practice the same time period to see how cold you will feel at the end. Back gas or nitrox mix up to 40% or air is a better alternative to argon. Also this avoids the ridiculous argon bottle (often filled with air :-)

With regard to the construction of dry suits…consider the following, where will you be spending most of the dive? Probably doing decompression…If this is not the case…it doesn’t matter what suit you wear! If you do complete long decompressions…6-8mm Neoprene will keep you warmest for longest. Compressed neoprene or tri laminates are lighter and “possibly” more comfortable on the surface, but these types of material have virtually no insulating properties and rely heavily on under suit selection. You will not get any heavier at maximum depth with a neoprene suit compared with a membrane suit. If you can dive a membrane or crushed neoprene without an under suit, you probably don’t need the drysuit in the first place. Undersuits at depth definitely compress as much as thick neoprene! Drysuits make very poor back up buoyancy alternatives, unless you are wearing the lightest of tanks in warm water. Consider a dual bladder wing.

If you can, wear a wetsuit. This fixes the urination/hydration issue also ;-)

For dives shallower than 60m for no longer than 20minutes…then any training manual, and, virtually any decompression program will give you a fairly reliable ascent plan.

For deeper dives: Keep the Helium as low as experience allows, When choosing decompression gases, when you make a raise in oxygen, drop the helium by this amount. You must keep the nitrogen % constant or dropping. Keep helium in the decompression gas right up to the oxygen stop at 3-4m. By keeping your decompression Po2 less than 1.4 you will avoid making po2 breaks (air breaks.)

Air breaks, while decompressing on oxygen, from a Trimix dive may cause type 1 bends later, due to counter diffusion (on extreme dives). Counter diffusion will cause far worse bends during a deep decompression stop (type 3 and 2) if the decompression gas contains insufficient helium and the ascent ceiling is violated or near.

Decompression Table Design

Decompression table designers used to work for large, often government backed organisations and institutions. Names that deepened the well of decompression understanding are well known and respected. Haldane, Workman , Buehlman and the many others that have furthered our understanding spent many years analysing decompression data taken from men working in hyperbaric environments both dry and wet, and then refining the results to reflect what needed improving. Much of the research into decompression theory has been driven by the oil industry and commercial diving companies. Additionally many navies around the world have seen the tactical benefits in understanding the inter action between man and the undersea environment. These two large research entities have made big leaps with the knowledge to descend a person deep underwater and return them safely and undamaged.

Since the drive for oil production has largely turned to remote and robotic means, and the navies have realised that the risk/reward equation is unbalanced when sending human beings without protection against the massive pressures found underwater, the need for refined decompression data has dried up. Divers could be reasonably assured by the research conducted in the past, and the fact that the tables were validated during actual experiments on men and woman.

The dive profiles that technical divers call routine are quite unlike the controlled dives that commercial and military divers repeat everyday. Decompression theory is advancing at a much slower speed than the desire to descend deeper and longer by technical and recreational divers. In the last 10 years a new breed of decompression “experts” are emerging, they offer untried and un tested methods that are propagated through the internet to a hungry audience.

Some of the new decompression techniques are based around traditional decompression algorithms that, with a few modifications can be reliable when used conservatively. Other table designers have ventured completely away from historically validated methods and have marketed radical decompression algorithms that received no verification through human testing. Unfortunately the designers of decompression software are very happy to let their customer base be the testers of the product.

Decompression injuries can occur instantly or manifest themselves over years. Divers wishing to dive outside traditional methods of decompression should take time to understand the implications, and attempt to analyse the ascent plan using knowledge from truly experienced divers or software products designed to compare past human based test data with newer math based alternatives. The decompression analyser ”DecoChek” developed by Stephen Burton is an excellent tool for divers to obtain decompression plan comparisons and analysis data.

There are many versions of dive software on the market. Models based on dissolved gas theories have many verification dives. The models based on free gas elimination, have been tested in various net experts imaginations only. Free gas models will slowly merge with traditional models over time, as the their bends incidence increases. Free gas models are associated with very deep stops that actually increase decompression loading later, that they don't compensate for. They have been poorly validated mainly during moderate dives to 90m. While you might not get bent using them everytime, your bones and circulation will suffer in the long term. This is the reason that the developing scientists discontinued work on these models in the late 1970’s! The IT specialists that have reincarnated them recently, are interested in your cash now, not your arthritis later…you have been warned ;-)