Diving Risks

The best way to keep divers safe is to know the diving risks. An immediate obstacle to human activity under water is the fact that human lungs cannot naturally function in water environment. So, scuba diving is affected by two conditions: the pressure underwater and the air divers breathe.

The Pressure Underwater While Diving

Because water is denser than the air, while we descent the pressure will increase. This will create a problem for any air-filled spaces like the mouth, ears, para-nasal sinuses and lungs. This is because the air in those spaces is reduced in volume when under pressure.

Diver Equalizing Ears

Pressure affecting our ears while diving

At the beginning of the descent, an inability to equalize air pressure in the middle ear with outside water pressure can cause pain, and the tympanic membrane can rupture at depths under 3 m /10 ft. If not properly equalized.

To avoid this pain divers must equalize their ears while descending by pinching their nose and blowing really slowly through it. A practice of this exercise is recommended once before the dive and during the descent as many times as necessary.

Pressure affecting our para-nasal sinuse while diving

When ascending or going up your ears and para-nasal sinus spaces will released the pressure automatically.

Being congested will increased the diving risks and can affect your ability to equalize your ears and release the pressure from ears and para-nasal spaces when ascending. You should avoid diving if when not feeling well.

Pressure affecting our lungs while diving

While we descent the pressure increases and this affects the gases by decreasing the volume of them. See examples 1 and 2. Example 1 represents a bottle at the surface and example 2 a bottle at 20m / 66ft with 3 Bar/ 3 Ata of pressure. While we ascent the opposite happens, bringing the bottle back to its normal size.

But diver's lungs are not like the bottle because we are breathing underwater through the scuba gear. So, what really is affected are the volume and the density of the gases in our body.

Now imagine that we put air in that bottle at a depth of 20m / 66 ft and start ascending. The pressure will now decrease and the volume will increase creating a pressure inside the bottle that may make the bottle explode at the surface. This is the reason why to prevent diving risks, divers with scuba gear never hold their breath while scuba diving, making this the first rule of scuba diving - Always Breathe, never hold your breath. And due to this reason divers when ascending always do so very slowly. Take as a reference your computer or the little bubbles you are exhaling and never go faster than the smallest ones.

Example 1 (at the Surface)

Example 2 (at depth of 20m / 66ft)

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What we are trying to avoid by breathing normally and continuously while slowly ascending is an air embolism (gas or air bubbles in our vascular system), which is a more severe hazard at shallow depths if a diver ascends as little as three feet without venting the expanding gas volume in the lungs.

We will explain why. At 10 m / 33 ft below the surface the pressure is double (2 Bar / 2 Atmospheres) the pressure at the surface. This will decrease the volume of gases by haft (1/2) and at 20m / 66 ft (3 Bar / 3 Ata) will decrease the volume of the gases only by one third (1/3). Making the ascent from 10m /33 ft to the surface the most dangerous phase of the ascent.

The density underwater is also effected the same way as pressure. Pressure increases as density increases, requiring more of the molecules of the gases to fill the same space.

DepthPressureGas VolumeDesity

The effects of pressure on gas density

Why I breath more the deeper I go? It is all on how the pressure affects the gasses you breathe. See the next table: the deeper you go the pressure and density increasses, but the volume of gasses will decrease. Making you need more air on every breath you take.

For this reason divers need twice the air at 2 Bars / 2 Ata, at 3 Bars / 3 Ata divers will breathe three times the air at the surface. The deeper we go the more gases we use, increasing the diving risks.

Exact calculations or predictions on how long an individual's dive can last are impossible due to the factors like cold, stress, fitness and experience.

The Gases We Breathe While Diving

Air Composition

A lot of people think, that the gas divers breathe while scuba diving is oxygen. Although the human body needs oxygen to survive, under pressure oxygen can be toxic. So, the gas divers use from the tank is compressed normal air.


Air is composed of 78.084% of nitrogen, 20.946% of oxygen and 1% of other gases that have little or no effect when breathing compressed air. That's the reason a lot of instructors explain the composition of the air as 79% nitrogen and 21% of oxygen.


Nitrogen is the most abundant gas in the atmosphere, but is not used by humans during respiration. This gas can cause serious issues while diving and increase the diving risks.

Nitrogen under high pressure can temporally effect our nervous system and interfere with signal transmissions, causing at greater depths (30 to 40 meters/100 to 133 feet) the condition known as nitrogen narcosis. The effect is similar as being under the influence of alcohol (loss of decision-making ability, loss of focus, impaired judgment, multi tasking and coordination).

The most straightforward way to avoid nitrogen narcosis and create further diving risks is for a diver to limit the depth of dives. If narcosis does occur, the effects disappear almost immediately upon ascending to a shallower depth.

addition to its narcotic effects, nitrogen also brings another issue that adds to the diving risks. We mentioned already that our body does not use nitrogen during the respiration while scuba diving. Under pressure nitrogen dissolves into body tissues and starts to accumulate. This must be kept within limits to prevent nitrogen from coming out of solution and forming bubbles inside our body, known as "decompression sickness" or "the bends".

Pain and skin rash frequently in the limbs and joints, is the most common symptom of decompression sickness. Numbness, dizziness, weakness and fatigue are also very common symptoms to watch for.

The primary first aid for decompression sickness is to administer oxygen and lie the patient on his left side. Rapid decompression treatment in a chamber has proven highly effective in reducing or preventing permanent injuries.

To avoid the bends divers must minimize the water pressure on the body slowly at the end of each dive. This will allow the gases trapped in the bloodstream to gradually break solution and leave the body. This is done by ascending slowly and making safety stops or decompression stops using dive computers or decompression tables for guidance.

Knowing the time limits for each depth will avoid decompression sickness" or "the bends or other diving risks.

Diving Computer Diving planers or tables

The use of diving computers and tables will keep you save and will help avoid diving risks.

Mixture Of Gases

you can see while scuba diving, dives are limited in time and depth due to the nitrogen. Today thanks to the new technology we have managed to extend our limits. For those divers that exceed 40 meters/132 feet and for divers who need to spend a lot of time under water, a different gas mixture, training and equipment are required.


Technical dive is when divers carry more than one cylinder, containing different gas mixtures for a distinct phase of the dive (descent, bottom, and decompression). These different gas mixtures may be used to extend bottom time, reduce inert gas narcotic effects, and reduce decompression times.

The most commonly used mixture is Enriched Air Nitrox, which is air with extra oxygen, often with 32% or 36% oxygen (called EAN32 and EAN36, or Nitrox32 and Nitrox36, or Nitrox I and Nitrox II). This mixture, of course, with less nitrogen, will reduce diving risks and more important the decompression sickness. Due to the oxygen toxicity divers use nitrox only in dives where they need to spend a lot of time in depth less than 40 meters/ 132 feet, and also during the beginning of their descent to deep (or deeper) dives.

A mixture of oxygen with helium that also reduces the percentage of nitrogen is known as trimix. The lower density of helium reduces breathing resistance at depth allowing the gas mix to breathe safely on deep dives. This mixture is often used during the deep phase of technical diving and in deep commercial diving. For example, a mix named "trimix 10/70" consisting of 10% oxygen, 70% helium,

20% nitrogen is suitable for a 100 meters (330 feet) dive, but it cannot be safely used at shallow depths. Heliox, a mixture of 21% oxygen and 79% of helium is also used for deep dives.

Because sound travels faster in Helium than in air, during the deep dive, divers with communication systems have very high-pitch voices, which may be hard to understand to people not used to it.

...So, how to keep it safe and avoid diving risks?

Remember that being underwater has limits and risks that professional divers are willing to take. It is important to remember that recreational scuba diving is for fun. Dives between 5 to 20 meters/ 16 to 66 feet can show you the wonderful world that was once explored by Cousteau. These depths have the advantage that provide divers with better light, colours and marine life. Also during shallow dives you will breathe less air from the tank, making your dive longer and safer.

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