Section 1 Flashcards
How does pressure change as you go down?
1 bar per every 10 meters
Changes in pressure, air volume and density
Meters - Air volume - air density
10 1/2 x2
20 1/3 x3
30 1/4 x4
40 1/5 x5
Equalisation
Adding air to air spaces as you descend
When to equalise?
Every meter, before you feel discomfort
What to do when you cannot equalise
Signal and stop
Ascend slightly, try again
Stop if not working
Most important rule
Always breath, never hold your breath
What to do when you don’t have your regulator in your mouth?
Breath out slowly
Reverse squeeze
When expanding air gets trapped in a body air space during ascend
How long does your air last?
Follows the pressure/ volume relationship
Half as long at 10 meters under than on the top
1/3 as long as 20 meters compared to the top
Energy and breathing
More pressure = denser air = harder to breath = use more energy
Why does salt water cause more buoyancy?
Because it weighs more because of minerals in it
BCD
Buoyancy control device
Positive buoyancy
Floating
Object weights less than the water it displaces
Short cut buoyancy and air
More air = you expand = more volume = more buoyancy = up
BCD - reverse
Because when you ascend the gas you already have expands with less pressure, to you release / vent on your BCD to control your buoyancy
For descend, as pressure increases, your volume also decreases, reduces the water displaced, less buoyancy. Add air to your BCD to offset
Primary gear consideration
Suitability, fit, comfort
Why does your mask need to encompass your nose?
You need to blow air into your mask to equalise the pressure
Good mask
Sits close to your face for better vision
BCD Components
Inflatable bladder Cylinder band & harness/jacket Lower pressure inflator (lpi) Over pressure exhaust valve Weight system
Options: Buoyancy / lift Pockets D-rings Quick release / colours etc
Regular components
First stage/hub - connects supply to other competent s
Second stage - reduces first stage intermediate pressure to air you can breath. Deliver air only when you inhale + purge buttons to release air
Alternate air source / octopus - air for your buddy
Low pressure inflator (lpi) - supplies air into your hose
Submersible pressure gauge (spg) - indicates pressure remaining in your tank
Two aspects of weight system
- Right amount
2. Trim: horizontal position for floating
Vision and earring under water
Magnifies by a third, as water is more dense than air
You may see colour loss as you go down: red, yellow, green, blue
Sounds travels 4x faster
