Nitrox safer than air

[Scuba]

Scuba once bubbled...
Is there any conclusive evidence to support the claim that Nitrox reduces the incidence of DCS?
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Dr. Paul replied

Lots! there are even separate tables for Nitrox diving

I've moved this from another thread seems it seems this is the appropriate place for it.

How much safer than air is Nitrox?

How does the incidence of DCS compare at different depths?

Peter

 

[TexasMike]

I'll leap in here real quick to inform you (and the other readers) that questions such as this are usually covered in your Nitrox certification classes.

I have taken the TDI course and can specifically recommend it. And it does answers Scuba's questions.

 

[Scuba]

Fair enough Texas Mike.

Nonetheless, I would at least like to have some idea of what Nitrox has to offer. Does it reduce the risk of DCS by 1 % or 70 %, for example.

 

[O-ring]

http://www.scubaboard.com/t13547/s.html

 

[redacted]

Their answer to this question is that the risk of DCS when diving air is extremely low if you follow established procedures and restrictions. Therefor, the reduction in DCS due to nitrox is small at best. What you do get is more NDL time which you can use to increase safety margins and/or bottom time.

 

[jbd]

to do a search in the Ask Dr Deco section or maybe you should post your question about reducing the risk of DCS by any given percentage in that forum.

I seem to recall a very similar question being asked in the past but I don't think there was any definitive answer given.

It would seem to me that the level of risk reduction would depend on mix used, depth and time.

 

[Rick Murchison]

The idea of Nitrox is to take some of the huge oxygen toxicity safety margin and apply it to the lower nitrogen safety margin. We never get something for nothing, and to characterize Nitrox as "safer" carries many conditional qualifiers.
It's why we have a Nitrox specialty course.
Rick

 

[Stone]

Scuba once bubbled...
Nonetheless, I would at least like to have some idea of what Nitrox has to offer. Does it reduce the risk of DCS by 1 % or 70 %, for example.

Scuba,

Here's a way to get a ballpark figure on the safety margin you can get using Nitrox. Look at the attached graph. This graph shows the NDL for Air, EAN32, and EAN36. It also shows the limit imposed by using an 80 cf tank and a diver with a SAC of .57 (first dive of the day and square profile). If you look at a depth of 100 fsw, you will see the Air line allows about 20 min to NDL. The EAN32 line allows about 30 min to NDL.

Here's a real oversimplification (but this is a WAG): Assign the EAN32 NDL line a value of 0% safety margin and the X axis (zero time at any depth) a safety margin of 100%. If you dive EAN32 for 30 minutes at 100 fsw you have 0% safety margin. If you dive EAN32 on an Air table (20 minutes at 100 fsw), then EAN32 gives you a safety margin of 33% over Air (at 100 fsw).

(30 min - 20 min)/30 min = 1/3 = 33%

 

[Stone]

Further assumptions and explanations on the Air vs Nitrox graphs can be found on This Page of my website.

There is an HTML version that anyone can see (non-interactive), and a downloadable Excel version that lets the user change SAC rate (breaths per minute and lung volume) and tank size (gas volume).

 

[The Iceni]

I like the graphs, Stone.

I can even change the SAC figures to metric!