Adventure Dominica
What Is Nitrox
1. Nitrox? EANx? Enriched air? Everyone of us has breathed nitrox. Nitrox
means a mix of nitrogen and oxygen and the word "nitrox" doesn't tell the
relations of those elements. So air is nitrox too because it contains
(basically)
nitrogen (79%) and oxygen (21%). The base of word nitrox is the expression
Nx/Ox, where N is the chemical sign of nitrogen and O is the chemical sign
of
oxygen. So basically nitrox can be any mix of nitrogen and oxygen
containing
1 to 99 % of oxygen (and rest is nitrogen).
Enriched air oxygen means a nitrox mix which has more oxygen than air has,
so then the mix has 22-99% of oxygen. Enriched air nitrox has also shorter
name, EANx, where x is the percentage of oxygen, ie. EAN40 (40% oxygen
in
the mix). Also EANx40 label is used sometimes (the letter "x" is preserved in
the label). Usually people mean EANx when they say "nitrox", and so do I
further here.
However, it is important to the relations of enriched air nitrox and nitrox,
because nitrox can also be "hypoxic" mixture containg less oxygen than air!
Then we say that the mix is hypoxic, ie. it has less oxygen than 21%.
Hyperoxic nitrox is EANx, and normoxic nitrox is basically air, 21% of
oxygen
and 79% of nitrogen. Hypoxic mixtures are not recreational diving, but air
and
EANx usually are. For more information about different gases, take a look at
http://techdiver.ws/exotic_gases.shtml.
2. History of nitrox diving
In about the year 1890 scientics discovered to benefits of enriched air in
diving in theory. The first real mass diving tests were conducted during the
World War I and a little before. During the WW II it was used much more,
and
the first open circuit EANx equipment were used.
In the year 1979 USA's National Underwater and Athmospheric
Administration (NOAA) published EANx diving tables.
International Association of Nitrox and Technical Divers (IANTD) bas
established in the year 1985 (USA) and IANTD UK in 1992 (Europe). ANDI
and TDI were also quickly in markets.
In 1995 PADI (Professional Association of Diving Instructors) took nitrox
training as a part of it's training program, and the course certifies diver to
dive nitrox dives within the recreational limits and with blends of 22%-40%
of
oxygen.
3. Is nitrox safer than regular air?
This is one of the most popular myths regarding nitrox diving. People
usually
refer the avoidance of DCS (decompression sickness) when they claim EANx
to be safer than air.
Let's take a look at the diving accident statistics! DAN (Divers Alert
Network)
has statistics of DCS cases in the USA, which is based on DEMA/NUADC and
PADI New Diver Benchmark reports. According to them, the probability to
get DCS by air diving is about 0.004% (1 to 25000). Based on this number,
and on the PADI Undersea Journal 3/97 magazine, the probability to get DCS
by air diving even once during 500 dives is 1.98% (1 to 50). The risk is 1.49%
in nitrox diving in same amount of dives. So... so far the difference is
marginal, even though nitrox seems to be a bit safer.
But an accident doesn't have to be DCS only, and when diving with nitrox
there are several other concerns too that air diving doesn't have. Gas
blending, analyzing errors, oxygen clean equipments, CNS clock etc. may
also
be a source of accident. In this point I have to say that nitrox diving is not
dangerous when done right, but these points have to be counted when people
talk about safety. So nitrox diving is safe, but not safer than air, generally
speaking.
4. Myths
Besides the safety myth above, there are several myths regarding nitrox
diving:
People who don't know much about nitrox think sometimes that it is used
for
deeper dives. Well, it is not, but it is mostly used on mid deep dives, ranging
from 20-40 meters (~60-130 feet). The more oxygen you have in the mix,
the shallower will the MOD (maximum operating depth) be.
It is also a common misunderstanding to think that it causes less narcosis.
This would be due the fact that it has less narcotic nitrogen. But oxygen is
also narcotic, and according to some references it is maybe as narcotic than
nitrogen, and together with nitrogen it could be even more narcotic
(Bennett
1993, Inert Gas Narcosis, the Physiology and Medicine of Diving, 4th
edition)!
There are also no advantage in rare embolia cases (The Undersea Journal
3/97).
5. Why should one dive with nitrox?
Simply: to gain more bottom time and to have shorter surface time intervals.
For example, if you dive two dives to 20 meters (66 feet) with one hour
surface time, the no decompression limited bottom times will be 45 minutes
and 24 min, respectively. Now, if do the same with EAN40, will the bottom
times rise to 98 min and 61 min, respectively. (PADI diving tables)
Another example: Two 25 min dives to 25 meters (83 feet). The surface time
will be at least 2 h 19 min (in no decompression limits), but with EAN40
you
don't even have to have the surface time! (PADI diving tables)
EANx is also used in technical and commercial diving to shorten the
decompression times.
We offer NITROX, only to NITROX certified divers.
1. Nitrox? EANx? Enriched air? Everyone of us has breathed nitrox. Nitrox
means a mix of nitrogen and oxygen and the word "nitrox" doesn't tell the
relations of those elements. So air is nitrox too because it contains
(basically)
nitrogen (79%) and oxygen (21%). The base of word nitrox is the expression
Nx/Ox, where N is the chemical sign of nitrogen and O is the chemical sign
of
oxygen. So basically nitrox can be any mix of nitrogen and oxygen
containing
1 to 99 % of oxygen (and rest is nitrogen).
Enriched air oxygen means a nitrox mix which has more oxygen than air has,
so then the mix has 22-99% of oxygen. Enriched air nitrox has also shorter
name, EANx, where x is the percentage of oxygen, ie. EAN40 (40% oxygen
in
the mix). Also EANx40 label is used sometimes (the letter "x" is preserved in
the label). Usually people mean EANx when they say "nitrox", and so do I
further here.
However, it is important to the relations of enriched air nitrox and nitrox,
because nitrox can also be "hypoxic" mixture containg less oxygen than air!
Then we say that the mix is hypoxic, ie. it has less oxygen than 21%.
Hyperoxic nitrox is EANx, and normoxic nitrox is basically air, 21% of
oxygen
and 79% of nitrogen. Hypoxic mixtures are not recreational diving, but air
and
EANx usually are. For more information about different gases, take a look at
http://techdiver.ws/exotic_gases.shtml.
2. History of nitrox diving
In about the year 1890 scientics discovered to benefits of enriched air in
diving in theory. The first real mass diving tests were conducted during the
World War I and a little before. During the WW II it was used much more,
and
the first open circuit EANx equipment were used.
In the year 1979 USA's National Underwater and Athmospheric
Administration (NOAA) published EANx diving tables.
International Association of Nitrox and Technical Divers (IANTD) bas
established in the year 1985 (USA) and IANTD UK in 1992 (Europe). ANDI
and TDI were also quickly in markets.
In 1995 PADI (Professional Association of Diving Instructors) took nitrox
training as a part of it's training program, and the course certifies diver to
dive nitrox dives within the recreational limits and with blends of 22%-40%
of
oxygen.
3. Is nitrox safer than regular air?
This is one of the most popular myths regarding nitrox diving. People
usually
refer the avoidance of DCS (decompression sickness) when they claim EANx
to be safer than air.
Let's take a look at the diving accident statistics! DAN (Divers Alert
Network)
has statistics of DCS cases in the USA, which is based on DEMA/NUADC and
PADI New Diver Benchmark reports. According to them, the probability to
get DCS by air diving is about 0.004% (1 to 25000). Based on this number,
and on the PADI Undersea Journal 3/97 magazine, the probability to get DCS
by air diving even once during 500 dives is 1.98% (1 to 50). The risk is 1.49%
in nitrox diving in same amount of dives. So... so far the difference is
marginal, even though nitrox seems to be a bit safer.
But an accident doesn't have to be DCS only, and when diving with nitrox
there are several other concerns too that air diving doesn't have. Gas
blending, analyzing errors, oxygen clean equipments, CNS clock etc. may
also
be a source of accident. In this point I have to say that nitrox diving is not
dangerous when done right, but these points have to be counted when people
talk about safety. So nitrox diving is safe, but not safer than air, generally
speaking.
4. Myths
Besides the safety myth above, there are several myths regarding nitrox
diving:
People who don't know much about nitrox think sometimes that it is used
for
deeper dives. Well, it is not, but it is mostly used on mid deep dives, ranging
from 20-40 meters (~60-130 feet). The more oxygen you have in the mix,
the shallower will the MOD (maximum operating depth) be.
It is also a common misunderstanding to think that it causes less narcosis.
This would be due the fact that it has less narcotic nitrogen. But oxygen is
also narcotic, and according to some references it is maybe as narcotic than
nitrogen, and together with nitrogen it could be even more narcotic
(Bennett
1993, Inert Gas Narcosis, the Physiology and Medicine of Diving, 4th
edition)!
There are also no advantage in rare embolia cases (The Undersea Journal
3/97).
5. Why should one dive with nitrox?
Simply: to gain more bottom time and to have shorter surface time intervals.
For example, if you dive two dives to 20 meters (66 feet) with one hour
surface time, the no decompression limited bottom times will be 45 minutes
and 24 min, respectively. Now, if do the same with EAN40, will the bottom
times rise to 98 min and 61 min, respectively. (PADI diving tables)
Another example: Two 25 min dives to 25 meters (83 feet). The surface time
will be at least 2 h 19 min (in no decompression limits), but with EAN40
you
don't even have to have the surface time! (PADI diving tables)
EANx is also used in technical and commercial diving to shorten the
decompression times.
We offer NITROX, only to NITROX certified divers.