• Scuba Air Pressure
• Scuba Diving Risks
• Scuba Air Tanks
• BAR to PSI
• Atm (Atmosphere) To Bar Conversion
• Meters To Fathoms Conversion

Nitrox Mixes - Oxygen 100%
The MOD of 100% Oxygen is 6m.
This places you on the 1.6ata top limit. Do not go below for your own safety.

Pressure Equivalents
1 atm = 1.01325 bar = 10.337 meters (f w) = 33.9139 feet (f w) = 33.066 feet (s w)
1 bar = 0.986923 atm = 10.2018 meters (f w) = 33.4704 feet (f w) = 32.6336 feet (s w)
s w = Sea Water.
f w = Fresh Water

Approximate Pressure Equivalents Commonly Used in Diving
1 bar = 1 atm = 33 feet (s w ) = 10 meters = 14.7 p.s.i.

Scuba Air Pressure

Re-Printed from www.thescubaguide.com website

Air is massive. All around and above us we are "swimming" in air and the weight of the air above us exerts pressure on everything in it. We do not notice or feel the air pressure around us because our bodies are compressed and exert an equal force back.

The weight of the atmosphere exerts a pressure of 14.7 psi at sea level. In other words, a 1 inch column of air as tall as the atmosphere (about 50 miles) weighs 14.7 pounds. This unit is called 1 Atmosphere of pressure or 1 ATM.

Scuba divers are concerned with pressures in tanks, in heads, in masks and under the water. We know that water is much heavier than air, so it exerts higher pressures with less volume. A cubic foot of water weighs 62.5 lbs, whereas a cubic foot of air weighs 1/12 lb. Sea water is even heavier - a cubic foot of sea water weighs 64 lbs. To exert 14.7 psi (1 ATM) it takes 50 miles of air, whereas it only takes 33 feet of water to exert the same pressure.

Let's suppose you fill a balloon with 24L of air. Let's take it scuba diving.

You see that the volume of the air changed the most between 0 feet and 33 feet, where it was squished to half of its previous size; a loss of 6L. Descending from 33 feet to 66 feet changed the volume by only 2L. As our air goes deeper the relative compression decreases. You will experience this effect firsthand when scuba diving; the first 15 feet is when you'll feel "the squeeze" as all air spaces (lungs, sinuses, ear canals, the air in your mask, intestines and even bits of air trapped in your teeth) are compressed to half of their sea-level size. When descending you need to compensate for that loss of volume and "reinflate" your body by equalizing your ears, exhaling into your mask (which will literally suction itself to your face). You also need to add air to your BCD to maintain buoyancy. Once you're past 15 feet it gets easier and once you're below 40 feet you might hardly feel the difference in pressure at all.

The reverse holds true when ascending to the surface. All the air spaces will double in size in the last 33 feet; this means you need to leak out air as you ascend, bubbles will escape from your mask and you need to release air from your BCD; lest it inflate like a balloon and send you bobbing quickly to the surface (and probably give you the bends while you're at it).

Scuba Diving Risks

Scuba diving is not a dangerous sport. Scuba diving is riskier than a sport like hockey or baseball, but less dangerous than street luge or mountain climbing. Modern scuba diving equipment is easy to use, very reliable and with the proper training and a responsible attitude scuba diving can be enjoyed safely. In fact, almost all scuba diving injuries and casualties are the result of recklessness or bad judgment.

There are certainly risks involved in scuba diving. Part of certification training is learning about those risks and how to avoid them. The majority of possible health problems are forms of barotraumas, which are all caused in one way or another by changes in pressure. Other possible risks are associated with higher absorption of gases, while other risks are more mechanical and environmental in nature.

Here are some of the risks associated with scuba:

• Barotrauma (explained by Boyle's law)
• alternobaric vertigo
  Dizziness or disorientation caused by unbalanced pressures in the inner ear. Most commonly experienced by stubborn scuba divers trying to dive with the common cold.
• altitude sickness
  Headache caused by a quick ascent, usually associated with airplane travel.
• barodontalgia
  Pain caused by tiny bubbles of gasses trapped in the teeth, usually in fillings or caps.
• decompression sickness, a.k.a. "the bends"
  Nitrogen coming out of a solution in tissue which is caused by hastened decompression.
• dysbaric osteonecrosis
  Rare bone lesions produced by long term exposure to high pressure environments.
• embolism
  Nitrogen coming out of a solution in the body. It can be caused by accelerated decompression.
• arterial gas embolism
  Gas coming out of a solution in the arteries. It can be potentially fatal.
• cerebral embolism
  Gas coming out of a solution in the brain. It can be potentially fatal.
• lung expansion injury
  It can be caused by holding breath while ascending.
• pneumomediastinum
  Ruptured bronchus or alveoli in the lungs from excessive pressure. May be caused by holding breath while ascending.
• pressure arrhythmias
  Abnormal heart rhythms caused by external pressure.
• tinnitus, Eustachian & inner ear damage, Tympanic membrane rupture and/or hearing loss
  Inner ear damage can result from diving without equalizing air pressure in the Eustachian tubes. It is complicated or caused by water pressure and blocked sinuses and it can be extremely painful.

• Non-Barotrauma (explained by Henry's Laws and Dalton's Laws)
• co2 toxicity, a.k.a. hypercapnia.
  Too much CO2 in the body, usually caused by inadequate exhalation or air consumption during heavy exertion. Symptoms include shortness of breath, headache and/or confusion.
• nitrogen narcosis, a.k.a. "rapture of the deep"
  The result of a toxic effect of high pressure nitrogen on nerve conduction. Symptoms are comparable to the effects of alcohol drunkenness.
• o2 toxicity
  Toxic effects of absorbing too much oxygen. Symptoms include a burning sensation in the lungs, twitching, dizziness, vomiting and/or seizures.
• Other physical and health hazards - Scuba Diving
• dangerous marine life
  Most common injuries are the result of divers touching poisonous animals such as jellyfish, fire coral, urchins or stingrays. Attacks by large fish are extremely rare.
• dehydration
  Dehydration is an inadequate bodily water level. Surprisingly common on boat tours; diving while dehydrated aggravates other health risks including nitrogen narcosis and hypercapnia.
• hypothermia
  Hypothermia is a loss of body heat and early symptoms include fatigue and loss of judgment.
• drowning
  An obvious risk if for any reason a diver breathes in water instead of air or just simply the loss of air.
• running out of air
  Typically caused by irresponsible air management or scuba equipment failure.
• underwater injury
  Common injuries include abrasions and cuts (from sharp coral), sprains, bumps and bruises. Studies show more serious injuries occur getting in and out of the boat than actually in the water.

Scuba Air Tanks

Typical atmospheric air is mostly nitrogen (78%) and oxygen (21%) with only a small amount of carbon dioxide (0.03%). Other gases are present in trace amounts: Hydrogen, Argon, Neon, Helium and more.

When you breathe your lungs absorb oxygen from the air, but they also absorb all the other gases as well. The oxygen is used by your body for all its functions, but what about nitrogen? Air has more than three times more nitrogen than oxygen, so your body is dealing with quite a lot of it. The answer is that our body is saturated with inert nitrogen, it offgasses through your skin and quite a lot of it filtered by your organs and passed as nitrates in your urine.

When your tanks are filled for scuba diving they are usually filled with dry filtered air. Pumps and filters remove most of the particulates (dust, pollen, airborne pollutants). Water vapor is also present in air; the amount varying greatly depending on temperature, pressure and weather. Water condensation can rust the inside of a scuba tank, so water vapor is filtered as well. The result is a tank containing a normal mixture of dry atmospheric gases in normal proportions.

BAR to PSI

Reprinted from www.asknumbers.com

You may use this pressure conversion table if you are converting from bar to psi (pound per square inch) for the values listed in the table below.

For your information, Bar is the atmospheric pressure at the sea level, which equals to 100 kilopascals. Psi is 1 pound of force per square inch.

1 Bar = 14.5037738 Psi (Pound Per Square Inch)

To convert any other value, please go to website: Pressure Conversion

To convert pressure from psi to bar, please go to website: Psi to Bar

Bar to Psi Chart

Atm (Atmosphere) To Bar Conversion

You may use this pressure conversion table if you are converting from atm (atmospheric pressure) to bars for the values listed in the table below.

For your information, Atm (atmospheric pressure) is the force per unit area by the weight of air above that point. Bar is the atmospheric pressure at the sea level, which is around 100 kilopascals.

1 Atm = 1.01325 Bars

To convert any other value, please go to Pressure Conversion

Atm to Bar Chart

Meters To Fathoms Conversion

You may use this length conversion chart if you are converting from meters (m, metre) to fathoms for the values listed in the table below.

1 Meter = 0.546806649 Fathoms

1 Fathom = 1.8288 Meters

To convert any other value, please go to Length Conversions

Meter To Fathom Chart

Other useful sites for tables and pressure laws are:

www.scubamed.com.au/GasLaws/GasLaws.html

www.engineeringtoolbox.com/pressure-d_587.html

Disclaimer: The information listed here is the best possible source and if you need to use this information during any sporting activity then it is incumbent on each individual to confirm it’s accuracy.