Some Basic Nitrox Questions

[Snoweman]

Just use the Calc Nitrox app on your android.

 

[TMHeimer]

Possibly he just wants info. to decide whether to take the course or not. Who knows.
Anyway, regarding questions about depths and times, I imagine Nitrox tables are available somewhere online for some "exact" figures.

 

[Brett Hatch]

I'm considering nitrox as the next step, and will greatly appreciate some input on the following:

1. Is there rule of thumb for how much longer BT EAN32 and EAN36 offer, as compared to regular air, all else being equal?
2. Considering oxygen toxicitiy, what would be the depth limits for EAN32 and EAN36, as compared to the general depth limit of 120ft for recreational dives with regular air, all else being equal?

Thanks!

1. There is no good rule of thumb here since the underlaying math equation is complicated: it depends on more than 1 variable, and the relationships between the variables are not linear. But if you know how to use dive tables, you could get a sense of it by comparing a 21% air table to a 32% or 36% nitrox table. Or if you have an air/nitrox computer with a planning mode, you can get a sense of it by planning different profiles. I think you will find that at shallower depths (say under 60 feet) it will not really matter, since you'll run out of gas before hitting your NDL, regardless of gas. But in the deeper depths (60 - 120 feet or so), diving nitrox will very often get you significant extra bottom time.

2. On the other hand, the math on MOD is simple, and already answered upthread -- and covered in detail in a course. The thing to keep in mind when reading up on this is that different PPO2 values have been considered "safe," and have varied over time in different contexts. In my rec OC nitrox course I learned that 1.6 PPO2 is generally considered the ceiling of safety, and that diving with a planned 1.4 PPO2 max is a good idea to give a safety buffer. And most computers/shops/tables/classes I have seen around, use similar figures.

But you'll see old US Navy publications recommending 2.0, closed circuit rebreather divers recommending 1.0 to 1.2, hyperbaric chambers over 3.0. Point is, if you are thinking about doing this, it is important to learn it correctly for the context you will actually be diving in, so that you don't plug in a value that makes sense in a different context and get yourself hurt.

Diving nitrox correctly is very safe and not much more expensive than air. But there are some non-obvious risks that you really do need to understand, and you need to learn how to use an analyzer. The classes run a couple-few hours and cost like $150 or so. It sounds like you are trying to figure out of the class is worth the time/money, versus just continuing to dive on air. In my view if you do much diving in the 60-120 foot range (or intend to), taking the class is a no-brainer

 

[TMHeimer]

Most places I've shopped Nitrox is more than double the cost of Air. Like $14 vs. $6. To me that is significant. I guess one could easily figure out what an extra $16US ($20 CAD) comes to per minute of extra bottom time you get on a two tank charter trip.

 

[ATJ]

As your diving improves your air consumption will also improve and you will find that even on relatively shallow dives you run out of NDL before running out of air. Nitrox is great for those situations. It is worth doing the course (but it should be included in OW or at least AOW but isn't).

 

[TMHeimer]

As your diving improves your air consumption will also improve and you will find that even on relatively shallow dives you run out of NDL before running out of air. Nitrox is great for those situations. It is worth doing the course (but it should be included in OW or at least AOW but isn't).

Agree with all. Not sure how much your air consumption will improve, as I think that may depend on how "good" a diver you are at the start and first few dives-- and how regularly you dive early on.

 

[tursiops]

Most places I've shopped Nitrox is more than double the cost of Air. Like $14 vs. $6. To me that is significant. I guess one could easily figure out what an extra $16US ($20 CAD) comes to per minute of extra bottom time you get on a two tank charter trip.

To the contrary, many places I go the nitrox is free (no additional cost over air) or a negligible extra expense.

 

[DogDiver]

In North Florida nitrox is purchased by the cubic foot. As most cylinders never have less than 1,200 psi at the end of the dive. Twin cylinders is the rule. It’s cheeper to fill with nitrox. But again in North Florida low pressure steel cylinders are filled to 3,900 psi. Nobody never died in a cave for having too much gas to breathe.

 

[TMHeimer]

To the contrary, many places I go the nitrox is free (no additional cost over air) or a negligible extra expense.

Thanks. First I've heard of that, but I've only patronized maybe 5 shops over the years.

 

[Gareth J]

Thanks. First I've heard of that, but I've only patronized maybe 5 shops over the years.

Tom

A lot of the Red Sea operators supply Nitrox free on their liveaboards.
Partly its commercial, other operators do it so they need to follow suit to remain competitive. But mainly for safety, they are less like to have cases of DCI if everyone is using Nitrox, & those cases they get are likely to be less serious.

Gareth