Yesterday night I finally completed my Recreational Nitrox class. This allows me to get fills and use Nitrox mixes of up to 40% oxygen when I go diving. I figured since maybe one person that reads my blog is a diver I would explain the basic principles behind this and gas management in general.
When you first get certified as an open water diver, almost everyone learns while on compressed air. This consists of 21% oxygen, 78% nitrogen, and <1% other stuff (argon, CO2, hydrogen, etc.). We are taught to dive within what are called No-Decompression Limits (NDL). This name is in fact misleading, as all dives are decompression dives to some extent. The point of the NDL is that you can ascend safely to the surface without mandatory decompression stops with minimum risk of decompression sickness (DCS), more commonly known as the Bends.
The basic premise behind DCS is a law of physics called Henry's Law. Henry's Law states that as the partial pressure of a gas increases, it's solubility in liquid, in this case blood, increases proportionately. This becomes an issue with nitrogen as you spend time at depth and the amount of nitrogen absorbed into your tissue increases. As you ascend, the pressure decreases again and the nitrogen comes out of solution. When diving within NDL and ascending slowly, less than about 15 feet/min, the size of the bubbles coming out of solution are sufficiently small to usually avoid causing any problems. However, beyond NDL or with too rapid an ascent, larger bubbles can collect in joints, under the skin, or worst case scenario, in the brain, subsequently causing the symptoms of DCS.
Where Enriched Air Nitrox (Nitrox) comes in is increasing these no-decompression limits. With a higher percentage of oxygen in the mix, there is also less nitrogen. The lower nitrogen content of the mix means there is a lower partial pressure at depth, and slower absorption into the tissue. Therefore you can spend more time down with the same effect, or the same amount of time down with less effect from nitrogen than if you were on air. Non-harmful effects of nitrogen include narcosis, which is similar to mild anaesthesia at depth, as well as a nitrogen "hangover" afterwards.
Contrary to what many people think, Nitrox does not allow you to dive deeper. It is actually classified as a mid-level gas, most useful from around 60 feet down to around 110 feet based on what mix you use. Beyond those limits you actually run the risk of oxygen toxicity. This is caused when the partial pressure of oxygen in the mix exceeds around 1.6 atmospheres, or 1.6 times the pressure exerted by air at sea level. Oxygen at high enough pressures is actually extremely dangerous and can even cause convulsions. For this reason, when diving Nitrox, you must be aware of the maximum operating depth of your mix. This is a concern not often covered with air, because the MOD of that is around 190 feet, well beyond the scope of recreational diving. However, when used with care and proper planning, Nitrox can make for a very enjoyable and safe dive.
Just remember, friends don't let friends dive air.
-Z
Showing posts with label diving. Show all posts
Showing posts with label diving. Show all posts
Monday, March 2, 2009
Thursday, November 20, 2008
Philosophy of Diving
OK, so perhaps I jumped into the details too quickly on that last post. I apologize, I just started writing about the first thing that came to my head when I was going to write an article about learning to dive, Rule number 1 seemed a natural place to start. But now I realize I must go back even farther for people to understand why I dive.
Aside from the television shows and movies you see growing up with divers jumping in the water and blowing up sharks with oxygen tanks, my first real encounter with diving was in high school. My freshman biology teacher, Mr. Lopatka, sponsored a Spring Break dive trip to Bimini each year. I would have loved to go on those trips, but alas, we never really had the money for me to take them (I kind of used up my share going to Ireland in '01). Nevertheless, a young lady who would eventually become one of my closest friends did get certified as a PADI Open Water diver and began furthering her diving education.
And so it passed, high school went on and was a good time for the most part. I made some awesome friends, watched three kickass football seasons, played horn under 3 different directors and 2 principals, but never did learn how to dive. That's all good, there's not much diving at the US Air Force Academy anyways. Now the Academy was an experience in itself, and there's a whole blog about that here so I will not get into the gory details. I was signed up to take a dive class my firstie year, but never got that far before I left the Academy and returned to Florida.
I took a semester off and began working at Best Buy to get a little spending cash until I went back to school. Well it turns out that I really like cameras, and I'm genetically predisposed to talking to everyone I meet, so Best Buy worked out rather well. I continued working there while I went to school at UCF in the spring, then upon my acceptance to UF for fall semester I transferred up to the Gainesville store and started working there over the summer.
Enter my new supervisor, Lance Briner, new to the camera business as well as new to Best Buy. It's all good, I'm more than happy to pass on knowledge I've acquired from my previous store because we're all on the same team. Well it turns out that before Lance became supervisor, he actually owned his own dive shop. He is also certified as an instructor in almost anything you can think of. So, through this series of fortunate events, I ended up with one of the best instructors around and I will probably never meet a person that is more passionate about diving than him.
Now, to the important part of the post, yes I know it was a long time coming but here it is: Why I Dive. I do not dive to go deeper than someone else, nor do I dive so I can look cool or act macho. I do not dive to push the limits, nor do I dive to prove anything to anyone. The reason is simple; I dive because when I am underwater I feel a sense of freedom and being alive that I feel very few other places. It is soaring through the sky with nothing but the air holding you up, and it is floating through 3 feet of powder as the third track down Alberta Peak. It is riding the melody of the horn as it seems to play itself, and it is painting a picture of the world as you see it through the lens of the camera. That is why I dive.
In the end however, the best part of the dive is always hanging out with my buddies afterwards. It's getting home to my family or calling them up on the phone just to tell them I love them and I miss them. Never will I do anything during the dive that would jeopardize those things afterwards. There is nothing under the water or in a cave that is worth losing that. If I ever lose sight of that, it is time for me to stop doing what I'm doing, whether it be diving, flying, skiing, or even playing my horn. But right now I am living life and loving life.
That is why I dive.
-Z
Aside from the television shows and movies you see growing up with divers jumping in the water and blowing up sharks with oxygen tanks, my first real encounter with diving was in high school. My freshman biology teacher, Mr. Lopatka, sponsored a Spring Break dive trip to Bimini each year. I would have loved to go on those trips, but alas, we never really had the money for me to take them (I kind of used up my share going to Ireland in '01). Nevertheless, a young lady who would eventually become one of my closest friends did get certified as a PADI Open Water diver and began furthering her diving education.
And so it passed, high school went on and was a good time for the most part. I made some awesome friends, watched three kickass football seasons, played horn under 3 different directors and 2 principals, but never did learn how to dive. That's all good, there's not much diving at the US Air Force Academy anyways. Now the Academy was an experience in itself, and there's a whole blog about that here so I will not get into the gory details. I was signed up to take a dive class my firstie year, but never got that far before I left the Academy and returned to Florida.
I took a semester off and began working at Best Buy to get a little spending cash until I went back to school. Well it turns out that I really like cameras, and I'm genetically predisposed to talking to everyone I meet, so Best Buy worked out rather well. I continued working there while I went to school at UCF in the spring, then upon my acceptance to UF for fall semester I transferred up to the Gainesville store and started working there over the summer.
Enter my new supervisor, Lance Briner, new to the camera business as well as new to Best Buy. It's all good, I'm more than happy to pass on knowledge I've acquired from my previous store because we're all on the same team. Well it turns out that before Lance became supervisor, he actually owned his own dive shop. He is also certified as an instructor in almost anything you can think of. So, through this series of fortunate events, I ended up with one of the best instructors around and I will probably never meet a person that is more passionate about diving than him.
Now, to the important part of the post, yes I know it was a long time coming but here it is: Why I Dive. I do not dive to go deeper than someone else, nor do I dive so I can look cool or act macho. I do not dive to push the limits, nor do I dive to prove anything to anyone. The reason is simple; I dive because when I am underwater I feel a sense of freedom and being alive that I feel very few other places. It is soaring through the sky with nothing but the air holding you up, and it is floating through 3 feet of powder as the third track down Alberta Peak. It is riding the melody of the horn as it seems to play itself, and it is painting a picture of the world as you see it through the lens of the camera. That is why I dive.
In the end however, the best part of the dive is always hanging out with my buddies afterwards. It's getting home to my family or calling them up on the phone just to tell them I love them and I miss them. Never will I do anything during the dive that would jeopardize those things afterwards. There is nothing under the water or in a cave that is worth losing that. If I ever lose sight of that, it is time for me to stop doing what I'm doing, whether it be diving, flying, skiing, or even playing my horn. But right now I am living life and loving life.
That is why I dive.
-Z
Rule Number 1
So in light of my mother finding another article outlining why I should not SCUBA dive, I would like to put up a post every once in a while explaining why putting on a giant rubber suit, strapping 60 pounds of gear on my back and proceeding to breath underwater for anywhere from 30 minutes to several hours is merely an absurd idea and not a dangerous one.
Rules of diving:
Rule number 1: Never hold your breath (mostly for ascending, just easier to remember this way)
This was the first rule Lance told us when we started our Open Water class. It was probably because it was the one that applied to us standing in 3 feet of water. Reasoning behind it is while underwater, you are breathing compressed air. The air then enters your lungs at a pressure corresponding to the depth you are diving at. For those of us who have had physics or fluids or thermodynamics lately, for a gas PV=nRT. n (number of moles of gas), R (Universal Gas Constant), and T (Temperature) remain constant throughout this whole process (negligible differences, so it's a safe assumption). Therefore Pressure and Volume are inversely proportional at all times.
When standing at sea level, the atmospheric pressure is appx 101 kPa, 1 atm. That is caused by the weight of about 80 miles of air stacked on top of us. Now water, being about 1000 times denser than air, exerts much more pressure than air as we descend through it. For this reason, we reach a pressure of 2 atm at 33 feet below the surface of the water. That means the 33 feet of water above us is exerting the same weight on us as the 80 miles of air above it. It also means that the same amount of air at 33 feet takes up half as much space as it did at the surface. By the same logic, if you fill up your lungs at 33 feet (represented by a balloon), when you ascend to the surface holding your breath, the volume doubles and, as succinctly put by my instructor, Lance Briner, "Pop, pop."
In conclusion, don't hold your breath, it's bad. That's kind of why it's rule number one.
SO, there's your first lesson on things that I've learned and now have zero ability to forget that keep me safe while I'm underwater. There will be more posts, perhaps tonight if I can't sleep. I fly out to El Salvador in 30 hours, so I'm rather excited right now.
Dive safe.
-Z
Rules of diving:
Rule number 1: Never hold your breath (mostly for ascending, just easier to remember this way)
This was the first rule Lance told us when we started our Open Water class. It was probably because it was the one that applied to us standing in 3 feet of water. Reasoning behind it is while underwater, you are breathing compressed air. The air then enters your lungs at a pressure corresponding to the depth you are diving at. For those of us who have had physics or fluids or thermodynamics lately, for a gas PV=nRT. n (number of moles of gas), R (Universal Gas Constant), and T (Temperature) remain constant throughout this whole process (negligible differences, so it's a safe assumption). Therefore Pressure and Volume are inversely proportional at all times.
When standing at sea level, the atmospheric pressure is appx 101 kPa, 1 atm. That is caused by the weight of about 80 miles of air stacked on top of us. Now water, being about 1000 times denser than air, exerts much more pressure than air as we descend through it. For this reason, we reach a pressure of 2 atm at 33 feet below the surface of the water. That means the 33 feet of water above us is exerting the same weight on us as the 80 miles of air above it. It also means that the same amount of air at 33 feet takes up half as much space as it did at the surface. By the same logic, if you fill up your lungs at 33 feet (represented by a balloon), when you ascend to the surface holding your breath, the volume doubles and, as succinctly put by my instructor, Lance Briner, "Pop, pop."
In conclusion, don't hold your breath, it's bad. That's kind of why it's rule number one.
SO, there's your first lesson on things that I've learned and now have zero ability to forget that keep me safe while I'm underwater. There will be more posts, perhaps tonight if I can't sleep. I fly out to El Salvador in 30 hours, so I'm rather excited right now.
Dive safe.
-Z
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