Wednesday 31 July 2013

Dive with the Devil... on the Devil's Gas!!

This is the image I use to stamp people's log book when they come diving with me. I think it is quite apt, since I always dive on, what was once considered to be, the Devil's Gas

Nitrox was actually one of the first specailties I took after certifying as a Scuba Diver. At the time, I had no idea how useful and well-used this certification would be but with time, it has become apparent.
What is Nitrox?

Nitrox is quite simply air, with a bit more Oxygen added!!

Back to school science, you may remember that the normal air that we breathe is made up of around 78% Nitrogen and 21% Oxygen with a few other gases that barely make up 1% and so are negligible. For the sake of ease, we say 79% Nitrogen and 21% Oxygen.


Nitrox contains more Oxygen, so something must be removed from the mix to accommodate for it. So, we have more Oxygen and less Nitrogen! As you can see in the diagram above, 32% Nitrox contains 32% Oxygen and 68% Nitrogen.

What's the benefit?

Think back to your initial Scuba Diving Training and Decompression Planning. The gas in your breathing mix, which limits your time underwater is Nitrogen.

While we breathe underwater, we have a certain amount of time we can stay at depth before our bodies have absorbed enough nitrogen that a direct ascent to the surface would not be possible. If we overstay this time limit, we have to complete decompression stops (as opposed to the Safety Stop that we all make in recreational diving) to prevent the nitrogen coming out of our bodies too fast and forming bubbles (decompression sickness).

By reducing the amount of Nitrogen in the gas we breathe, we can extend the amount of time we can spend at depth. With 32% nitrox, you can spend almost twice as long at 30m than you can when you breathe air!

Some Divers believe that nitrox makes them feel less tired after multiple dives than they would if they were breathing compressed air, although I don't think there is any substantial evidence to prove nitrox has any great influence on this. It is more of a personal thing

The biggest health benefit for Divers Diving Nitrox comes into effect when you dive Nitrox on air tables.

This means you take the conservatism of diving on air (shorter no decompression limits) but have the added "buffer" of increased Oxygen in the mix. This means the diver stays that bit further away from Decompression Limits and should be better for the Diver!!

Although, be aware, if you are using Dive computers set to air while you are in fact breathing Nitrox, you must know your Maximum Operating Depth so you do not accidentally exceed it because your computer says you can!

What's a Maximum Operating Depth?

Oxygen is not a deep Diving gas. In fact, the deeper we go, the less Oxygen we can use. Deep Divers, heading down to 100m will use a hypoxic breathing gas with around 12% Oxygen, which is too little oxygen to be breathed at the surface.

This is because, Oxygen becomes toxic when breathed at certain pressures. So we must know the Maximum Depth (MOD) we can safely dive our breathing mix to.

Nitrox is perfect though for the recreational limits between 15 and 40m and Divers must work out their MOD for the mix they are breathing. For example, 28% nitrox can be safely breathed down to 40m, whereas 32% nitrox can be safely breathed to a depth of just 33metres.

This all comes with the training.

For multiple diving around the 30m range, I don't think you can beat diving with Nitrox, simply for the benefit of the added time you get to spend underwater enjoying the sites and wrecks and it is definitely becoming more mainstream today.

All the major agencies now offer Nitrox training courses and it is, not suprisingly, one of PADI's best selling specialties.

So, if Nitrox is the Devil's gas, I am certainly the Devil...Gas me up!!!


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