1. DALTON’S LAW
Total pressure equals the sum of the partial gas pressures in a mix.
TP = P1+P2+P3+P4 ETC
To find Partial pressure multiply total pressure by the percentage of the gas in question.
Nitrogen being 80%, Oxygen being 20%
Atmospheric pressure being 15 PSI
Nitrogen 15 X .80 = 12 PSI
Oxygen 15 X .20= 3 PSI

3. PARTIAL PRESSURE DEPTH PRESSURE NITROGEN OXYGEN SURFACE 1 ATA 15PSI
33 FEET
2 ATA 30 PSI
24 PSI
6 PSI
66 FEET
3 ATA 45 PSI
36 PSI
9 PSI
99 FEET
4 ATA 60 PSI
48 PSI
132 FEET
5 ATA 75 PSI
60 PSI
15 PSI

4. DALTON’S LAW EFFECTS
We are affected by both total pressure and partial pressure. Too much or too little of a gas can be harmful
NITROGEN: The largest amount of gas we breathe. Two affects both negative. Determines how long we can stay under water.
Decompression sickness
Narcosis: Caused by depth. Starts at about 100 feet.
Problem solving issues
Not consistent
Go shallower to stop. No after affects
This should be considered dangerous and avoided

5. Nitrogen Narcosis When nitrogen is under pressure it can produce an effect on your body also called “rapture of the deep”.
At depths approaching 24 meters (80 feet).
Oxygen toxicity:
Carbon Monoxide Toxicity:
At depths approaching 24 meters (80 feet).
Nitrogen can be intoxicating, impairing judgment.
Recovery is as simple as ascending to a shallower depth.
Oxygen toxicity:
Pure oxygen at depths below 7.5 meters (25 feet).
The percentage of oxygen in regular air is not toxic until well below the sport diving limit of 40 meters (130 feet).
Carbon Monoxide Toxicity:
Is formed by incomplete combustion of a petroleum products such as gasoline or oil.
Symptoms include nausea, blue lips and nail beds, confusion, headache, and unconsciousness.
Pure oxygen and medical attention are the proper treatment.

6. OXYGEN: keeps us alive can get to little or to much.
Excessive O2 or poisoning can be caused by diving to deep or adding O2 to your tank
Deep diving is not a concern at this point.
Why would we add O2 to our tanks
NITROX is adding O2 to a scuba tank to allow us to stay under for longer times.
We can not dive as deep with NITROX
32%=110 feet 36%=90 feet
Dive tables allow 55 min at 60 feet. 32% allows 100 minutes at 60 feet.
On repetitive dives we see 4 times more dive time

7. Excessive O2 can cause convulsions at depth
To dive with NITROX you must take a NITROX course. This is usually 2 nights and can be taken while in your basic course.
Underwater world offers this course monthly.
CARBON MONOXIDE: Odorless, colorless gas resulting from petroleum combustion.
To much of this is lethal.
CO attaches to hemoglobin 200 times better than O2. So we have a problem as the amount of CO goes up more hemoglobin carries it and leaves the O2 20 PPM is considered lethal

8. Let’s see how this works
Surface 5PPM safe
33 Feet 2 times/ breath 10 PPM safe
66 Feet 3 times/ breath 15 PPM safe
99 Feet 4 times/ breath 20 PPM UNSAFE
Air that is safe on the surface becomes lethal at depth.
Prevention: Only fill tanks at a dive shop. Shops filter the air and remove moisture.
SYMPTOMS: Blue lips and fingernails.
Medical emergency. Bring to surface and give O2 if available. Must be take to hospital for treatment

9. CARBON DIOXIDE: We produce this gas through metabolism
CARBON DIOXIDE: We produce this gas through metabolism. Our bodies take in O2 our cells use it and produce CO2 as a byproduct.
CO2 causes us to breathe Our brain monitors CO2 not O2. Lack of O2 and we pass out.
Excess CO2 result of bad air or improper breathing.
BAD AIR: always get fills at dive shops. If air smells or taste funny do not use return to dive shop and let them know.
IMPROPER or SKIP BREATHING
Taking a breath and holding it before taking another breath. To prolong air usage or equal someone else’s air consumption.
ON SCUBA NEVER HOLD YOUR BREATH

10. WHY: Large person with small person, in shape with out of shape, experienced with novice.
As we skip breathe CO2 builds up and at some point we have to get rid of it by hyper ventilation. This defeats the air saving.
SYMPTOMS: At the end of the dive you have a raging headache
FIRST AID: Allow person to breathe fresh air
If after a dive everyone has a headache might be bad air. If one person they were doing something wrong.

11. SHALLOW WATER BLACKOUT: passing out in shallow water
Caused by excessive hyperventilation prior to breath hold dive.
CO2 causes us to breathe. Brain monitors CO2 build up and triggers the breathing reflex to lower the CO2 in our system.
When we dive the brain monitors this build up and also how long it will take to get back to the surface.
When we hyperventilate we lower the CO2 but do not increase the amount of O2. 3 PSI in air.
During a dive before the CO2 builds up enough the O2 level will fall. When our brain tells us to go up its too late. Some where on the way up in shallow water the O2 level will drop below 1 PSI and we will pass out.

12. PREVENTION: Do not excessively hyperventilate. No more than 3 breaths.
Never dive alone or at same time with buddy.
Don’t see how long you can stay underwater without someone watching
FIRST AID: Bring person to surface a resuscitate (mouth to mouth)
AIR CONSUMPTION
FACTORS: Fitness, work load, stress, warmth, body size, skills, comfort, euphoria

13. HOW MUCH AIR WILL YOU USE: Surface air consumption rate or SAC rate
Go to a know depth and convert to atmospheres. Stay for a period of time and note amount of air used. Divide air use by time and then convert to surface.
Covert depth to ATA. (Depth / 33) + 1
We go to 33’ (33/33)+1 = 2
We stay for 10 Minutes and use 800 PSI / 10 = 80 PSI per minute
Now go back to surface 80 / 2 = 40
Your SAC rate is 40 PSI / minute

14. HOW LONG WILL A 3000 PSI TANK LAST US AT 90 FEET
Convert 90’ to ATA (90/33) +1 = 3.72
Now multiply SAC by ATA 40 X 3.72 = per min
We would use 149 PSI per min as resting at 90 feet
Now divide 3000 PSI by 149 = 20.2 minutes
This is a resting rate so the tank will not last that long. ACR is not in stone will change with effort or temp
You can also do this while swimming to give a a working rate. You must stay at same depth while swimming.
This is covered more in depth in the NAUI advanced course