|author||Bryan Newbold <firstname.lastname@example.org>||2018-08-10 16:01:16 -0700|
|committer||Bryan Newbold <email@example.com>||2018-08-10 16:06:46 -0700|
refactor under outdoorsing
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-Self Contained Underwater Breathing Apparatus
-SCUBA stands for "Self-Contained Underwater Breathing Apparatus".
-One of the primary organization regulating recreational SCUBA diving is
-PADI (the Professional Association of Diving Instructors).
-:BCD: The buoyancy control device is basically an inflatable live vest
- that you can inflate using the regulator (or by mouth) to control
- your buoyancy. Your buoyancy changes as you use up air (tank gets
- lighter for same volume displaced), inhale/exhale, swim in water
- of different temperature or salinity, or change depth: increased
- pressure compresses any flexible air pockets, including the BCD
- itself, neoprene foam, or a dry-suit.
- Most BCDs have their own pressure hoses coming from the first stage
- regulator that supply air.
- Sometimes there is only one vent valve, which has to be at the
- highest orientation or air will not vent out of the bladders.
-:Tank: Most tanks are made of steel or aluminum and can store compressed
- air of up to 3000psi. They are stored at pressure to prevent moisture
- from leaking in. There is a valve built into the tank itself that
- usually gets taken apart and repaired every two years. Tanks
- can last for decades even with heavy use; they are pressure tested
- for fatigue and leaks.
-:Regulator: The first-stage regulator is connected to the tank and steps
- the pressure down to about 250psi above the surrounding/ambient
- pressure. Hoses carry air at this mid-level pressure to the second
- stage regulator/mouthpiece, which steps the pressure down to
- about what is in your lungs. Depending on the regulator they can
- be stiff (you have to suck a bit to get air, but then it rushes
- in with force) or very natural feeling (air comes very smoothly
- on inhalation and doesn't press into your lungs).
-:Alternate: These days almost everybody carries a second regulator mouthpiece
- for emergencies. These are always on and ready to breath from,
- but usually stiffer so they don't free-flow as often.
- A dive computer monitors time and depth to give you an accurate picture
- of how much excess nitrogen is in a diver's bloodstream. By
- continuously integrating they usually "give more time at depth" than
- hand calculations using tables (which err towards safety).
-:Dry Suit: A dry suit is a sealed and air tight, keeping the diver's skin dry.
- Extra insulation is needed to give warmth underneath. Some dry
- suits are made of compressed neoprene.
- A dry suit has to be constantly adjusted with tank air just like
- the BCD to maintain inflation and buoyancy.
-:Wet Suit: Wet suits work on the principle of holding water against the skin:
- a diver's body warms this water and stays cozy as long as water
- flow is restricted enough. Even little bit too much flow through
- wrist or ankle openings can be very cold.
-A PADI Open Water Diving course gives a recommended limit of 20m/60ft.
-A "deep dive adventure course" gives a recommended limit of 30m/100ft,
-and additional experience gives a limit of 40m/130ft.
-With careful decompression stops and enriched compressed air (higher oxygen
-content) it's possible to reach depths of hundreds of meters. Sometimes
-commercial divers will dive for many hours using surface supplied air,
-then live at the surface in a compression chamber overnight between dives
-to stay at the same pressure [*]_.
-I'm pretty sure `Jacques Cousteau`_ invented the aqualung, which is the basis
-for modern diving, but I'll have to check.
-.. _Jacques Cousteau: /k/jacquescousteau/
-After a regular no-decompression dive, wait at least 12
-hours before flying (or going to high altitude, eg over 300m).
-.. [*] Need a citation, heard this word of mouth