Nitrox course. What's the point?

[ginti]

Dody... Nitrox 32% means I get longer times to NDL and is better over repeated dives. However dive times still depend on your sac rate and how long you stay at depth. If I was using nitrox 32% staying at 30m depth for 24 minutes I do not exceed NDL and can ascend and finish the dive. If on air at 30m can stay for 15 minutes but that is then 0 NDL so for safety lets make it 12 minutes at 30m on air. Nitrox gives me longer time to stay deep. It does not change the sac rate. So on multiple dives where you want to go deep to 30m then you get longer times to NDL. Even when I dive with my friends are also good on gas consumption we do not push staying deep on our dives. Sometimes we use nitrox but leave our computers on 21%. Some DM guides will do this as well.

I am not sure if I understand the meaning of your answer... The discussion here is about the advantages of nitrox, and I think that @EFX (and others as well) said it right. If one has problems because of gas consumption, the **short-term** solution is not to avoid nitrox: it is to use bigger tanks! If the gas consumption is too high, the optimal **long-term** solution would probably be to reduce the consumption itself. But the advantages of nitrox are always there, so the details about consumption are off-topic.

Am I missing something?

 

[David Novo]

@Dody bear in mind that the algorithm of your dive computer is more conservative than the one of the Perdix (that @BLACKCRUSADER is using) so it is likely that you will have shorter NDLs.

 

[Blackcrusader]

@Dody bear in mind that the algorithm of your dive computer is more conservative than the one of the Perdix (that @BLACKCRUSADER is using) so it is likely that you will have shorters NDLs.

Oops yes I forget about that sometimes it's also why I have to remind other divers to dive to their own computer. Some have found their computers locked them out for exceeding NDL on their computer and they missed the deco stop required. But that really means they didn't pay attention to their dive computer.

 

[Blackcrusader]

I am not sure if I understand the meaning of your answer... The discussion here is about the advantages of nitrox, and I think that @EFX (and others as well) said it right. If one has problems because of gas consumption, the **short-term** solution is not to avoid nitrox: it is to use bigger tanks! If the gas consumption is too high, the optimal **long-term** solution would probably be to reduce the consumption itself. But the advantages of nitrox are always there, so the details about consumption are off-topic.

Am I missing something?

Well if someone writes you get a longer dive time because they are using nitrox that can be misinterpreted. Nitrox won't give me longer dive times it gives me longer times to NDL. If you are at a place that only has AL80's then divers do not always get a choice about using bigger tanks. Many people fall under the assumption they can suddenly get longer dive times by using nitrox. All I was pointing out that your sac rate does not change by using nitrox and Dody does understand about sac rates.

Another member wrote The advantage that is stated most often is that it gives you more dive time when doing multiple dives per day which can be misunderstood. If I am on nitrox 32% and stay at 20m for the whole dive on an AL80 most vacation divers will never reach NDL they will be out of air first.

 

[Divin'Papaw]

Well if someone writes you get a longer dive time because they are using nitrox that can be misinterpreted. Nitrox won't give me longer dive times it gives me longer times to NDL. If you are at a place that only has AL80's then divers do not always get a choice about using bigger tanks. Many people fall under the assumption they can suddenly get longer dive times by using nitrox. All I was pointing out that your sac rate does not change by using nitrox and Dody does understand about sac rates.

Recreational dive times are always limited by either NDL or Gas. It is a good thing to point out. I would hope that even a green diver would "get" that but it is always a good idea to be explicit. If you are finding that your dives are always being limited by available breathing gas instead of NDL than Nitrox will be of little value to you.

As an example. The vast majority of my dives are in a HP100 in the 40-90' range and I have a respectable SAC (.40-.45 cfm on average). If I were to dive air my dives would ALWAYS be turned by NDL. By using nitrox given the diving I do my dive times are increased significantly. However, these facts don't apply to everyone. It is important to understand the parameters under which you are diving to assess how valuable Nitrox will be to you.

 

[ginti]

Well if someone writes you get a longer dive time because they are using nitrox that can be misinterpreted. Nitrox won't give me longer dive times it gives me longer times to NDL. If you are at a place that only has AL80's then divers do not always get a choice about using bigger tanks. Many people fall under the assumption they can suddenly get longer dive times by using nitrox. All I was pointing out that your sac rate does not change by using nitrox and Dody does understand about sac rates.

Another member wrote The advantage that is stated most often is that it gives you more dive time when doing multiple dives per day which can be misunderstood. If I am on nitrox 32% and stay at 20m for the whole dive on an AL80 most vacation divers will never reach NDL they will be out of air first.

Ok, got what you mean, fair point

 

[Blackcrusader]

Recreational dive times are always limited by either NDL or Gas. It is a good thing to point out. I would hope that even a green diver would "get" that but it is always a good idea to be explicit. If you are finding that your dives are always being limited by available breathing gas instead of NDL than Nitrox will be of little value to you.

Well in lots of vacation spots with vacation divers I am not limited on air but by the air consumption of other divers as the DM will try to get people shallow so they can complete at least 50 - 60 minutes. When I dive with my friends then a lot of dive centers will let you dive to either max time 75 minutes or 40 bar which ever comes first. Some places will let you rent tanks and you do your own dives.
I'm pretty sure Dody is aware he is a bright chap even though new to diving. So as I stated Nitrox lets you stay deeper with longer times to NDL but air consumption still controls the max time for the total dive time. Plus there is the max depth when on nitrox to factor in so if Dody wants to do a dive to 40m he would do that on air not nitrox.

 

[Divin'Papaw]

Well in lots of vacation spots with vacation divers I am not limited on air but by the air consumption of other divers as the DM will try to get people shallow so they can complete at least 50 - 60 minutes. When I dive with my friends then a lot of dive centers will let you dive to either max time 75 minutes or 40 bar which ever comes first. Some places will let you rent tanks and you do your own dives.
I'm pretty sure Dody is aware he is a bright chap even though new to diving. So as I stated Nitrox lets you stay deeper with longer times to NDL but air consumption still controls the max time for the total dive time. Plus there is the max depth when on nitrox to factor in so if Dody wants to do a dive to 40m he would do that on air not nitrox.

I get it. I'm agreeing with you.

One more benefit to consider. Even if your dive is limited by your air consumption Nitrox will give you an added safety factor. Less nitrogen loading is always good even if your dive is turned by your air consumption. Less nitrogen in your blood equals added safety factor assuming all other diving guidelines (MOD, ascent rate, safety stop) are followed. This is another reason I always dive Nitrox. Not the primary reason, but just another reason.

 

[Blackcrusader]

Ok, got what you mean, fair point

Thanks.

I often see divers who tell me they are doing Nitrox so they can get longer dive times. It's a common mistake when people do not understand they get longer times to NDL at depth rather than dive time itself. Staying deeper for longer they are going to get shorter dive times I am nitrox certified but even when using nitrox I am often on 21% setting on my dive computer. If I have a dive partner good on air consumption then sure switch to 32% whatever is needed and do some dives staying at depth for longer. Also sometimes the DM has to tell others in the group that fat bloke and his friend are doing their own things not exceeding NDL but will stay deeper than others on the dive.

Funny but true on my 93 minute dive posted the wreck is only a few hundred meters from the shore line I got out with the DM. The boat goes back to pick up an instructor and Advanced students. The instructor and students are back on the boat after 60 minute dive but they have to wait for use to finish our dive. So we get back on the boat and the students ask did we come out after them? I replied no we came out before them and we were the two guys deeper you waved at during your dive. They were quite startled that we were deeper and had a 33 minute longer dive than they had. I just told them I sip my air like a good champagne. Imagine if I had an AL 100 or 120 instead I could do that wreck on nitrox and do a 2 hour dive lol.

 

[Blackcrusader]

I get it agreeing with you. One more benefit to consider. Even if your dive is limited by your air consumption Nitrox will give you an added safety factor. Less nitrogen loading is always good even if your dive is turned by your air consumption. Less nitrogen in your blood equals added safety factor assuming all other diving guidelines (MOD, ascent rate, safety stop) are followed. This is another reason I always dive Nitrox. Not the primary reason, but just another reason.

The answers I write are really for Dody as he is the one asking. Your point is certainly valid as well.

As I wrote sometimes I use nitrox but leave computer in 21% setup. One place I dive with insists I do at least one dive on nitrox per day if doing 3 dives a day. I will probably start doing nitrox more often for dives 30m depth or less. If I was doing a liveaboard I would definitely use nitrox as you don't get many inexperienced divers and many liveaboards have dives only on nitrox unless doing tec dives. I often spend the last 10 - 15 minutes at 5m - 8m I don't do the ride NDL till low on air then a safety stop then out of the water. ( well on the rare occasion )