SCUBASCUBA : Effects of : Effects of Dissolved GasesDissolved Gases

Pascal’s PrinciplePascal’s Principle

•Pressure applied to fluids is Pressure applied to fluids is equally transmitted in all equally transmitted in all directions, to all parts of the directions, to all parts of the fluid and to all parts of a fluid and to all parts of a container.container.

•Think toothpaste…Think toothpaste…

Pascal’s principle = a fluid Pascal’s principle = a fluid distributes the force in all distributes the force in all directions equally directions equally

Hydraulic(fluid) brakesHydraulic(fluid) brakes

Consider: Consider:

• Hold your hand out straight… you Hold your hand out straight… you have more air on top of your hand have more air on top of your hand than under it… do you feel a than under it… do you feel a difference? difference?

• If you go to the bottom of the pool,… If you go to the bottom of the pool,… do you feel the weight pushing do you feel the weight pushing straight down? straight down?

• You dive down 900ft (300m) into the You dive down 900ft (300m) into the ocean… what does it feel like? ocean… what does it feel like?

Summary – Pascal’s Summary – Pascal’s principleprinciple

Pressure in water (any fluid) is Pressure in water (any fluid) is distributed equally. So if you are distributed equally. So if you are deep in water… you are squeezed deep in water… you are squeezed from all sides, not just from the top!from all sides, not just from the top!

Effects of pressure Effects of pressure on lungs – Free on lungs – Free divingdivingAt the surface At the surface

1atm & 6 liters1atm & 6 liters10m down (33ft)10m down (33ft)

2atm & lungs ½ the size 2atm & lungs ½ the size now, 3 litersnow, 3 liters

30m down (99ft)30m down (99ft)4atms & lungs 4atms & lungs squeezed to ¼ … 1.5 squeezed to ¼ … 1.5 litersliters

How deep has a human dived How deep has a human dived on one breath of air? on one breath of air?

214 meters / 702 feet. 214 meters / 702 feet. Total time was 5 minutes.Total time was 5 minutes.

Record swimming under water is 8 min Record swimming under water is 8 min 30 seconds, but that was “constant 30 seconds, but that was “constant depth”depth”

Most divers use SCUBAMost divers use SCUBA

S – SelfS – Self

C – ContainedC – Contained

U – UnderwaterU – Underwater

B – Breathing B – Breathing

A – ApparatusA – Apparatus

AKA – breaking air from a compressed air tank. AKA – breaking air from a compressed air tank.

Why the pressurized air is Why the pressurized air is important?important?

1)1) More air in a small pack… can use it More air in a small pack… can use it for a whilefor a while

2)2) The pressure of the air can hold back The pressure of the air can hold back the water’s pressure so you don’t get the water’s pressure so you don’t get crushedcrushed

… … up to a point (only to about 140ft up to a point (only to about 140ft safely)safely)

Can the pressurized air be Can the pressurized air be dangerous also?dangerous also?Now, when you are down deep Now, when you are down deep

technology has put a lot air particles technology has put a lot air particles in your lungs. What will happen to in your lungs. What will happen to that air as you rise up and the that air as you rise up and the pressure is less? pressure is less?

You won’t like how it feels to have your lungs blown up this big!!

11stst danger of SCUBA danger of SCUBA

Rupturing your lungs as you come Rupturing your lungs as you come up!!!up!!!

If a diver ascends too quickly, they If a diver ascends too quickly, they will rip a hole in their lungs!will rip a hole in their lungs!

11stst danger of SCUBA danger of SCUBAHow do you avoid this? How do you avoid this? You ascend slowly, breathing out the whole You ascend slowly, breathing out the whole

way (or at least as much as possible) so way (or at least as much as possible) so you have the normal amount of air in you have the normal amount of air in your lung at the surfaceyour lung at the surface

Release gas slowly

The problem of breathing The problem of breathing compressed air #2compressed air #2

Higher pressure of gas in your lungs Higher pressure of gas in your lungs means your blood dissolves more gas!means your blood dissolves more gas!

How do they get the COHow do they get the CO22 in your water to in your water to make cokes?make cokes?

CO2 pressure pump

The problem of breathing The problem of breathing compressed air #2compressed air #2

The carbonation in your soda is put there The carbonation in your soda is put there and held there by lots of “pressure”.. and held there by lots of “pressure”.. And what happens if you release that And what happens if you release that pressure? (open the can?)pressure? (open the can?)

The problem of breathing The problem of breathing compressed air #3compressed air #3

Nitrogen gas:Nitrogen gas:

- Starts at 30m (90ft)- Starts at 30m (90ft)

- Feels like intoxication- Feels like intoxication

- Causes death most - Causes death most commonly because of commonly because of bad choices.bad choices.

Oxygen gas:Oxygen gas:

- Much more serious- Much more serious

starts at deeper levelsstarts at deeper levels

- Most common with Most common with mixed gases with high mixed gases with high levels of oxygenlevels of oxygen

- Effects are not as Effects are not as reversiblereversible

- Brain damage, Brain damage, blindness, blindness, convulsions…convulsions…

Both oxygen and nitrogen are toxic if you Both oxygen and nitrogen are toxic if you breathe them under pressure!!!!breathe them under pressure!!!!

Mixed gasesMixed gases

Normal air is what most SCUBA uses, Normal air is what most SCUBA uses, but to go deeper you must mess with but to go deeper you must mess with the mix of air you breathe down therethe mix of air you breathe down there

Air up here is 21% oxygen 78% nitrogen .99 % various other gases

Diving deep often requires mixes otherthan these %’s

But the view is amazingBut the view is amazing

BCD – Buoyancy Control BCD – Buoyancy Control DeviceDeviceThe BCD takes on The BCD takes on

some of the work some of the work so your lungs don’t so your lungs don’t do all the work.do all the work.

The work of the BCD The work of the BCD is to compliment is to compliment your lungs so the your lungs so the diver is “neutrally” diver is “neutrally” buoyant buoyant

Maintaining “neutral” Maintaining “neutral” buoyancy is trickybuoyancy is tricky

1)1) Positive buoyancy = floatingPositive buoyancy = floating

2)2) Negative buoyancy = sinkingNegative buoyancy = sinking

3)3) Neutral buoyancy = suspended … Neutral buoyancy = suspended … not going up or downnot going up or down