From 78da0322932f17ed4d5b54f630e4139752b12129 Mon Sep 17 00:00:00 2001 From: Bryan Newbold Date: Fri, 10 Aug 2018 16:01:16 -0700 Subject: refactor under outdoorsing --- outdoorsing/SCUBA.page | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 outdoorsing/SCUBA.page (limited to 'outdoorsing/SCUBA.page') diff --git a/outdoorsing/SCUBA.page b/outdoorsing/SCUBA.page new file mode 100644 index 0000000..6e15c52 --- /dev/null +++ b/outdoorsing/SCUBA.page @@ -0,0 +1,89 @@ +--- +format: rst +categories: +toc: no +... + +============ +SCUBA Diving +============ +--------------------------------------------- +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). + +Equipment +--------- + +: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. +:Dive Computer: + 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. + + +Depths +------ +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 [*]_. + +History +------- +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/ + +Flying +------ +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 -- cgit v1.2.3