Ocean Diver Lectures Flashcards
Benefits of BSAC Membership
Largest club in world Internationally recognised qualifications Diving Manual SCUBA magazine 3rd party Insurance Member's prices in shop
Benefits of diving with a branch
Branch support Planned diary of dives Range of diving buddies and interests Sharing the experience Branch dive trips and holidays
Aim of OD course?
Train a diver who can use 21%, 32% and 36% O2 mixes in controlled conditions to a depth of 20m under the supervision of a DM
Describe the OD course
7 lectures, theory assessment, 5 sheltered water, 5 open water
Describe atmospheric pressure
Weight of air in 1cm square column of the atmosphere
=1kg/cm^2
=1 bar
What is water pressure?
Water exerts pressure of 1 bar for every 10m of depth
What is absolute pressure?
= gauge pressure + atmospheric pressure
Describe the structure of a mask.
Has tempered glass, a frame and a flexible seal with adjustable strap
How big is a snorkel?
40-45cm long
20mm diameter
What is Boyles Law?
For a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume
What does SCUBA stand for?
Self Contained Underwater Breathing Apparatus
Describe when a cylinder is tested and to what standard.
BS/EN standard
Has a working and a test pressure
Hydraulic testing every 5 years
Visual every 2.5 years
What is the composition of our exhaled breath?
17% oxygen
4% CO2
79% nitrogen
What happens with a breath hold dive with hyperventilation?
O2 level to support consciousness begins high and drops, because CO2 level for stimulus to breathe doesn’t reach threshold
Describe the effects of diving on the ear.
Sound travels faster underwater - direction difficult to identify
Air spaces - ear drum, middle ear and Eustachian tube
Describe heat loss when diving.
25 times faster than air
Cold water increases rate of heat loss
End dive if getting cold
When do we need thermal insulation when diving?
20C+ = no suit required 10-20C = wetsuit or drysuit required 0-10C = drysuit required
What is sinus squeeze?
When there is no equalisation between sinuses and ambient pressure
Mucus membranes swell to relieve pressure
Blood vessels burst
Sinus pain
If a diver feels pain in sinuses during descent they should abort dive (indicative of damage to sinus nerves)
What is Archimedes Principle?
When an object floats in water it displaces a weight of water equal to its own weight