Exposure Protection while SCUBA Diving

by May 16, 2013 05/16/13
SCUBA Diving

Most of us have experienced a winter that brought on warmer temperatures than expected. I for one can’t say I minded it, and above average temps certainly make the rain here much more bearable. With all of that in mind though, the water temperatures have still fallen to reasonably chilly levels.

Most of us divers have to consider that unless you are diving in the tropics along the equator, you need some sort of exposure protection. So let’s take a look at a few methods for protecting your body from the brutal cold underwater by examining some fun facts about temperatures and the difference between wetsuits and drysuits.

The human body loses heat approximately 26 times faster in water than in air of the same temperature. For this reason, when diving in water temperature less than about 90 °F (32 °C), you must have some means to keep your body warm to prevent hypothermia. The most popular candidate for this task amongst divers across the spectrum is the wetsuit.

Wetsuit Function

If you’ve ever been diving, you have more than likely had to don a wetsuit. My instructors used to tell me, “Remember that there are two kinds of divers: The ones that pee in their wetsuits, and the ones that lie about peeing in their wetsuits.” This adage works on the old school thought that wetsuits use a thin layer of water between the skin and the neoprene material the suit is made of to keep the body warm. The seal in the wetsuit sleeves and neck are supposed to keep new water from seeping in and chilling the body. This fun little tidbit is actually FALSE!

The wetsuit keeps your body warm by heating the air bubbles in the neoprene itself. As a result, the more water that gets into your suit, the less effective it is. So it is not uncommon to see products like Skin Seals being sewn into suits in attempt to keep cold water from getting in.

Wetsuit Fit and Myths

There’s been a strange debate as to how a wetsuit is supposed to fit. A lot of this debate has been fueled from the incorrect assumptions of the “thin layer of water principle” as well as another common myth that suits either shrink or grow over time. So let’s dispel any wetsuit myths now.

First and foremost, the whole fitting issue is simple. Based on how a wetsuit traps heat, you want to select one that fits as close to the body as possible without giving you the body squeezes. This is a simple problem to avoid. A suit should be relatively easy to get onto your body with the neck and sleeves being increasingly difficult to slide over your hands.

SCUBA2

It was said in the old days to get a suit that fit larger but this is caused by the lack of availability of quality fabrics in the diving industry. Suits were less flexible and thus tended to squeeze in certain areas more so than today’s higher quality demand.

“Some wetsuits shrink and some wetsuits grow.” Well, if you say so. These claims are both false. The bottom line is that quality suits will not shrink or grow, but rather they will remain the same relative size for years and years. Unfortunately you can’t blame the dryer if your suit has shrunk (most suits can be machine washed). If your suit is fitting a bit snug after the holidays, a running regimen can help your suit fit a little better, I know I need it.

Now if you remember the gas laws article we put up here some time ago, then you may be familiar with Boyle’s Law. Boyle’s Law states that “given a constant temperature, the volume of a gas varies inversely as the absolute pressure.” Then you may be asking, what if I go deeper and those little gas bubbles we talked about decrease in size? You know the answer to that based on logic, the suit becomes less effective and that is why most technical divers turn to the drysuit.

Drysuits

Drysuits are a wonderful tool for those that want to take on a more adventurous or complex style of diving. Regardless of the quality of your wetsuit, eventually they simply cannot hang on to your expectations when you decide to go deeper, colder, or longer. Drysuits are much more complicated to dive with and require an actual training session to be comfortable, but the end result is a more enjoyable dive and some gawking from the other guys on the cattle boat. Let’s talk about how the drysuit works.

Drysuit

Plain and simple, the drysuit keeps you warm based on the clothing you decide to wear underneath it. The suit itself provides no real insulation property, but rather provides the users with a dry climate so that the user can choose appropriate garments to wear inside and a thin pocket of air between the skin and material. I’m not referencing all of the other fancy items out there like the neoprene drysuit, or the semi dry suit, I am talking about the fabric suit that you layer over cold weather garments to protect you from the elements.

This suit is generally fitted for the wearer, slightly oversized to accommodate more layers of clothing underneath. The suit consists of fabric and rubber to produce a watertight barrier with tight rubber seals at the ankles, wrists and neck as well as a waterproof zipper either across the chest or down the back. Rear entry suits require the aid of another diver to be properly donned. Once inside however, the diver is just about ready to hit the water.

Remember earlier when we referenced Boyle’s Law? This Law is a nuisance to the drysuit diver because as the gases between your body and the wall of the suit contract, they will try to suck water in through the seals. Drysuits have little plastic circles on the arms and chest that act as inflators and purge valves. This allows the diver to connect an inflator hose to his suit and force air in to keep the pressure ambient and to act as a buoyancy compensator. Upon ascent, the diver simply purges the air from the suit using any of the purge valves installed and continues a slow and steady climb to the surface.

Dive Skin

When diving in waters that are warm enough to not require a suit, some divers opt for a dive skin. A skin is the diver version of what those of us in the industry refer to as under armor or base layer. It is a thin polyester material that helps reduce the likelihood of scratches, cuts, and rashes from sea life such as fish or coral. These tend to be flattering on the wearer unless you’re Daniel Craig, and provide virtually no insulating properties.

Disclaimer

ITS Tactical cannot be held responsible for any attempts at any form of diving without first seeking professional training and advice. The following article is not intended as a replacement for proper training and equipment used in any water sport activity. Diving is inherently dangerous, and introduces a unique set of risks not typically present in everyday life. We urge you to seek proper instruction from a qualified, and certified agency before attempting any sport requiring a life support system, namely: SCUBA. It is likewise very important that you contact your health care provider before attempting any training classes to ensure you are in good physical condition. Those with pre-existing medical conditions may be at a higher risk for certain complications that may become present while SCUBA Diving.


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GeorgeSmith
GeorgeSmith

yes i read the article very closely. i appreciate your thought about the scuba diving .

jason
jason

+1 on the gas bubbles in the neoprene issue. You are correct that water is not really part of the insulation, but the issue is keeping a minimal volume in the suit and preventing exchange through the openings. The semi dry suits I am familiar with are straight neoprene suits with neoprene seals (which don't seal as well) that are pressure compensated with an inflater. The whole purpose of insulation is to prevent thermal conduction. Gases are poor conductors, with the heavier gases being worse conductors and lighter gases being better conductors. This is why when diving HE mixes divers pretty much always use a separate inflation system, typically with Argon. HE being a better conductor will get you colder faster when breathing it, though with any compressed breathing gas it will be chilled due to expansion combined with evaporative cooling from the lungs since there is zero humidity in it. The Sherwood Oasis second stage helps a bit with this (Google it). I dive a DUI CF-300 (not a typo, I am a lucky DOG to have gotten a hold of one) and love it. I range from low quality thin fleece top and pants in warmer water (San Diego at depth is NEVER what you could call warm....) to good high tech silk weight thermal underwear and the high tech fleece jumpsuit when it is cold. Trapped gas combined with the insulating material properties make all the difference.

As to dive skins, the do provide a small amount of thermal protection by slowing the flushing of warmed water away from the body (Tri-laminate suits help even more). The bigger reason for them is abrasion and solar protection though.

The warmer you stay the slower your tissues will absorb gas. This can help give you an extra safety margin against DCS.

Interesting side note from a research paper I did in school: If you start coughing at depth STAY THERE!. 16psi can cause an overpressure injury to the lungs and the force of diaphragm contractions combined with expanding gas can easily exceed that. A gas embolism (bubble in the blood) can act as a seed nucleation point causing gas so be released from solution (like that spot in your beer glass that streams bubbles.....) The recorded cases of this happening to divers within 1/2 of the no decompression times (still safe to ascent directly to the surface by the tables) were all terminal when I did the research.

jason
jason

+1 on the gas bubbles in the neoprene issue. You are correct that water is not really part of the insulation, but the issue is keeping a minimal volume in the suit and preventing exchange through the openings. The semi dry suits I am familiar with are straight neoprene suits with neoprene seals (which don't seal as well) that are pressure compensated with an inflater. The whole purpose of insulation is to prevent thermal conduction. Gases are poor conductors, with the heavier gases being worse conductors and lighter gases being better conductors. This is why when diving HE mixes divers pretty much always use a separate inflation system, typically with Argon. HE being a better conductor will get you colder faster when breathing it, though with any compressed breathing gas it will be chilled due to expansion combined with evaporative cooling from the lungs since there is zero humidity in it. The Sherwood Oasis second stage helps a bit with this (Google it). I dive a DUI CF-300 (not a typo, I am a lucky DOG to have gotten a hold of one) and love it. I range from low quality thin fleece top and pants in warmer water (San Diego at depth is NEVER what you could call warm....) to good high tech silk weight thermal underwear and the high tech fleece jumpsuit when it is cold. Trapped gas combined with the insulating material properties make all the difference. As to dive skins, the do provide a small amount of thermal protection by slowing the flushing of warmed water away from the body (Tri-laminate suits help even more). The bigger reason for them is abrasion and solar protection though. The warmer you stay the slower your tissues will absorb gas. This can help give you an extra safety margin against DCS. Interesting side note from a research paper I did in school: If you start coughing at depth STAY THERE!. 16psi can cause an overpressure injury to the lungs and the force of diaphragm contractions combined with expanding gas can easily exceed that. A gas embolism (bubble in the blood) can act as a seed nucleation point causing gas so be released from solution (like that spot in your beer glass that streams bubbles.....) The recorded cases of this happening to divers within 1/2 of the no decompression times (still safe to ascent directly to the surface by the tables) were all terminal when I did the research.

Matthew Studley
Matthew Studley

I only dive with a drysuit these days. It allows for a much wider range of insulation which I can adjust depending on the conditions, redundant buoyancy, options for different inflation gasses with low thermal conductivity (such as argon), p-valve compatibility, protection from the wind on surface intervals without extra gear, sturdier footwear when gaining access to sites, being dry on the ride home, etc.

Eric
Eric

That is why I only dove with a drysuit (DUI CF200, TLS350, or Dive Rite). Even in the Florida Caves, where the temp is 72 degrees, that DS kept me warm at all times. And, the underlayer for the DS is key. wear to little and you get cold, wear to much and you over heaet.

James E
James E

I'm going to disagree with the bit about the seals on wetsuits. While they are not intended completely stop water from getting into the suit, they should be tight enough to keep water from freely moving in and out of the suit. If you look at Semi-dry suits the seals are more robust to let even less water in. Semi-dry suits are really just thicker wetsuits with tighter seals and waterproof zippers.

Also, just to point out to the other readers, the guy (is that you Brian?) in the drysuit is not wearing a diving dry suit, but a surface dry suit. it does not have the appropriate valves and inflators for diving. It looks to be one of the maritime assault suits (MAS) used by SEALs, EOD, SAR swimmers, etc.

Christian:

Nice DIY dry glove solution. Another solution to try when the temps aren't too low is to wear surgical gloves with your drysuit seal covering the gloves to keep water out, then using wetsuit gloves over those.

The AGA masks + a hood that fits correctly and can cover your face and fit over the edge of the face mask seal will make a huge difference in cold water. I've had to make dives in 43 degree water with only a wetsuit at work and keeping your head and face covered makes a huge difference.

James E
James E

I'm going to disagree with the bit about the seals on wetsuits. While they are not intended completely stop water from getting into the suit, they should be tight enough to keep water from freely moving in and out of the suit. If you look at Semi-dry suits the seals are more robust to let even less water in. Semi-dry suits are really just thicker wetsuits with tighter seals and waterproof zippers. Also, just to point out to the other readers, the guy (is that you Brian?) in the drysuit is not wearing a diving dry suit, but a surface dry suit. it does not have the appropriate valves and inflators for diving. It looks to be one of the maritime assault suits (MAS) used by SEALs, EOD, SAR swimmers, etc. Christian: Nice DIY dry glove solution. Another solution to try when the temps aren't too low is to wear surgical gloves with your drysuit seal covering the gloves to keep water out, then using wetsuit gloves over those. The AGA masks + a hood that fits correctly and can cover your face and fit over the edge of the face mask seal will make a huge difference in cold water. I've had to make dives in 43 degree water with only a wetsuit at work and keeping your head and face covered makes a huge difference.

Christian Nadeau
Christian Nadeau

I upgraded to a drysuit a few years after I got certified and I will never go back to wet unless I'm somewhere south of North Carolina (and even then it would still be an option). It was so nice being able to stay comfortable all year long, especially in December. I've also made up my own dry glove system (4" pvc pipes under the wrist seals, Harbor Freight sandblasting gloves over the wrist seals, held in place tightly with some vacuum o-rings, instructions can be found here >>> http://www.divematrix.com/showthread.php?4959-DIY-Drygloves-and-rings). When I get back into diving after college I hope to get an OTS Guardian or AGA Interspiro full-face mask so the only part of my body that will get wet will be parts of my head.

Felix L
Felix L

Two most important areas to keep warm while diving head and chest - get hoodie and vest.

decepticon
decepticon

I would like to know more about the concept of the wetsuit heating the gas bubbles to warm the body. This is not consistent with my research and years of experience as a marine biologist, but it has been a few years since I moved north and and there are many new materials with which I am unfamiliar. If body heat can warm the nitrogen bubbles in neoprene, why would the cooler, surrounding water not leach the heat away just as quickly?

In my experience, neither the thin layer of water nor the bubbles in the neoprene cause any heating of the body. The function of the neoprene is to insulate the body to retain as much of the heat generated by the body as possible. The ultimate goal is that neither the heat of the body or the cold of the surrounding water would be conducted into or through the bubbles in the neoprene. The function of the nitrogen bubbles is to slow the heat conductivity of the neoprene.

When it compresses at depth, the insulation properties are considerably diminished - which is why neoprene is not a good choice for deeper dives. Bardy, et.al, give the ratio of neoprene thickness and therefore conductivity being decreased by 50% at a depth of 50 ft., allowing heat to be lost at 3 times the surface rate. I am unfamiliar with the idea that the nitrogen bubbles themselves are heated by the body and therefore help warm the body.

I frequently dove in a wetsuit for work, mostly in warm Caribbean/Gulf waters in a medium weight wetsuit. I made a few dives in colder Pacific waters in a drysuit. In my experience, if I stayed down long enough, deep enough, I got really chilled in both configurations. Regarding the wetsuit diving, I discovered that for me, the biggest variable in retaining heat was wearing a well-fitted hood properly attached to my wetsuit and well situated with my facemask, and high-quality gloves and booties also properly attached to the wetsuit and/or sealed to me. None of this provided any extra heat, but it did insulate me better, allowing me to retain more of the heat created by my own body.

decepticon
decepticon

I would like to know more about the concept of the wetsuit heating the gas bubbles to warm the body. This is not consistent with my research and years of experience as a marine biologist, but it has been a few years since I moved north and and there are many new materials with which I am unfamiliar. If body heat can warm the nitrogen bubbles in neoprene, why would the cooler, surrounding water not leach the heat away just as quickly? In my experience, neither the thin layer of water nor the bubbles in the neoprene cause any heating of the body. The function of the neoprene is to insulate the body to retain as much of the heat generated by the body as possible. The ultimate goal is that neither the heat of the body or the cold of the surrounding water would be conducted into or through the bubbles in the neoprene. The function of the nitrogen bubbles is to slow the heat conductivity of the neoprene. When it compresses at depth, the insulation properties are considerably diminished - which is why neoprene is not a good choice for deeper dives. Bardy, et.al, give the ratio of neoprene thickness and therefore conductivity being decreased by 50% at a depth of 50 ft., allowing heat to be lost at 3 times the surface rate. I am unfamiliar with the idea that the nitrogen bubbles themselves are heated by the body and therefore help warm the body. I frequently dove in a wetsuit for work, mostly in warm Caribbean/Gulf waters in a medium weight wetsuit. I made a few dives in colder Pacific waters in a drysuit. In my experience, if I stayed down long enough, deep enough, I got really chilled in both configurations. Regarding the wetsuit diving, I discovered that for me, the biggest variable in retaining heat was wearing a well-fitted hood properly attached to my wetsuit and well situated with my facemask, and high-quality gloves and booties also properly attached to the wetsuit and/or sealed to me. None of this provided any extra heat, but it did insulate me better, allowing me to retain more of the heat created by my own body.

Elmernite
Elmernite

I have to say that I am with decepticon on this one. It's the basic concept that gas is a terrible conductor of heat. So surround yourself with a close fitting layer of gas trapped in a rubber matrix. Heat doesn't pass through it easily into the surrounding water.

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