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oxygen_rebreather [2024/05/31 20:44] – Explain ppo2 math better qlyoungoxygen_rebreather [2024/05/31 20:45] (current) – [why?] qlyoung
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 This question is most often asked by other divers. The funny thing is that the answer is usually obvious to non divers - it lets you breathe underwater! But when divers ask it, they mean something different. What they mean is "why would you buy a device with such limited utility?" I'll explain what they mean. This question is most often asked by other divers. The funny thing is that the answer is usually obvious to non divers - it lets you breathe underwater! But when divers ask it, they mean something different. What they mean is "why would you buy a device with such limited utility?" I'll explain what they mean.
  
-The thing about oxygen is that it's a highly reactive gas. This property is [[wp>Cellular respiration|critical to human chemistry]]. However, in excess concentrations, [[wp>oxygen_toxicity|oxygen becomes toxic]]. Therefore in a breathing gas you have to keep the oxygen concentration below a certain level in order to avoid poisoning the user. In diving, we do this by limiting the [[wp>partial_pressure|partial pressure]] of oxygen (ppO2). The "maximum" ppO2 generally accepted to be "safe" is 1.6 ATA. Oxygen partial pressure increases with depth. For pure oxygen, at the surface (where pressure is 1 ATA) your breathing gas is already at 1.0 ppO2. Every 33ft of freshwater adds another atmosphere of pressure, so for pure oxygen a ppO2 of 1.6 is reached at about 20ft. In short, you cannot safely dive an oxygen rebreather below 20ft. In some respects this is quite limiting; most dive sites are deeper than 20ft.+The thing about oxygen is that it's a highly reactive gas. This property is [[wp>Cellular respiration|critical to human chemistry]]. However, in excess concentrations, [[wp>oxygen_toxicity|oxygen becomes toxic]]. Therefore in a breathing gas you have to keep the oxygen concentration below a certain level in order to avoid poisoning the user. In diving, we do this by limiting the [[wp>partial_pressure|partial pressure]] of oxygen (ppO2). The "maximum" ppO2 generally accepted to be "safe" is 1.6 ATA. Oxygen partial pressure increases with depth. For pure oxygen, at the surface (where pressure is 1 ATA) your breathing gas is already at 1.0 ppO2. Every 33ft of freshwater adds another atmosphere of pressure, so for pure oxygen a ppO2 of 1.6 is reached at about 20ft. In short, you cannot safely dive an oxygen rebreather below 20ft. In some respects this is quite limiting; most dive sites are deeper than that.
  
-So why would you want one of these things? Well, for starters, not *everything* worth diving is deeper than 20ft. There are some sites, like [[https://diveatlas.org/index.php/Blue_Heron_Bridge|Blue Heron Bridge]], that are considered world class and have plenty to see in an o2rb's depth range. Also, not every dive has to have an objective. You can have a very enjoyable dive and never go below 20ft! For dives like that, the oxygen rebreather is awesome, better than open circuit. Because exhaled gas is captured within the system instead of being exhaled as bubbles, bubble noise is eliminated and the unit is almost completely silent (you can still hear the sound of oxygen pushing through the breathing hoses, but it's very quiet). Consequently aquatic life is much less scared of you.+So why would you want one of these things? Well, for starters, not *everything* worth diving is deeper than 20ft. There are some sites, like [[https://diveatlas.org/index.php/Blue_Heron_Bridge|Blue Heron Bridge]], that are considered world class and have plenty to see in an oxygen rebreather's depth range. Also, not every dive has to have an objective. You can have a very enjoyable dive and never go below 20ft! For dives like that, the oxygen rebreather is awesome, better than open circuit. Because exhaled gas is captured within the system instead of being exhaled as bubbles, bubble noise is eliminated and the unit is almost completely silent (you can still hear the sound of oxygen pushing through the breathing hoses, but it's very quiet). Consequently aquatic life is much less scared of you.
  
 The unit is also very lightweight. Fully assembled and ready to dive it weighs 6kg (~13lb) including an oxygen bottle (and not counting ballast). Compared to a typical OC scuba system, where the most basic equipment configuration exceeds 40 pounds (not counting ballast), it is much easier to transport. It's also much smaller, both in storage and in the water. In the water it's as close as you can get to wearing nothing at all. This makes it very enjoyable to dive. The unit is also very lightweight. Fully assembled and ready to dive it weighs 6kg (~13lb) including an oxygen bottle (and not counting ballast). Compared to a typical OC scuba system, where the most basic equipment configuration exceeds 40 pounds (not counting ballast), it is much easier to transport. It's also much smaller, both in storage and in the water. In the water it's as close as you can get to wearing nothing at all. This makes it very enjoyable to dive.
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oxygen_rebreather.1717188262.txt.gz · Last modified: 2024/05/31 20:44 by qlyoung
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