What's the difference - MOD / TOD?

[ardhill]

Hi

I understand what MOD - Maximum Operating Depth is, but someone mentioned to me about calculating the Target Operating Depth of a Nitrox mix the other day.

I Googled a bit, but still can't figure out what the difference is and what TOD is actually telling me. Can anyone shed some light on this for me please?

Thanks
.

[Andy the Coastie]

Time Of Dive ....... perhaps

[DannyB]

Originally Posted by ardhill

Hi

I understand what MOD - Maximum Operating Depth is, but someone mentioned to me about calculating the Target Operating Depth of a Nitrox mix the other day.

I Googled a bit, but still can't figure out what the difference is and what TOD is actually telling me. Can anyone shed some light on this for me please?

Thanks
.

I stand to be corrected but I suspect they are one and the same thing....

[ardhill]

Originally Posted by Andy the Commie

Time Of Dive ....... perhaps

No Andy, he was definitely talking about Target Operating Depth. That phrase is in a few diving related sites, but it looks a bit like calculating the MOD to me. DannyB may be correct, but I am not sure, so thought that I would ask. I figured that if I knew, then maybe next time, I won't feel so much of a prat saying "the what"?
.

[DannyB]

Originally Posted by ardhill

No Andy, he was definitely talking about Target Operating Depth. That phrase is in a few diving related sites, but it looks a bit like calculating the MOD to me. DannyB may be correct, but I am not sure, so thought that I would ask. I figured that if I knew, then maybe next time, I won't feel so much of a prat saying "the what"?
.

To coin a phrase "The only silly question is the one that's not asked", the only other thought I had was that one may be 1.4bar (TOD) and one 1.6 (MOD) but not sure.

Danny

[Roobydoo]

Its a language thing.

For example under PADI, the MOD (max operating depth) is PPO2 of 1.4, with the Contingency operating depth being 1.6

Under IANTD, the TOD, [i]Target Operating Depth[i], is usually 1.4, with the Maximum operating depth being 1.6

HTH

Steve

[garygee]

Hi folks

Well my understanding of MOD and TOD is as follows.
(this is show how little I really know)

TOD or target opperating depth is the depth at which you plan your PPO2 at, maybe you plan a PPO2 of 1.3 at depth X
This is where your dive should end up if all goes to plan.

MOD maximum opperating depth the the depth at which you maximum PPO2 is not exceeded maybe a PPO2 of 1.6
This is your known safety margin so you know if you have problems/dont stick to your dive plan, where your PPO2 is getting high.

Its to me a way of planning better and allowing a bit of safety into what ends up a real dive rather then a planned dive. One (TOD) is where you PPO2 to be with a bit of safety margin, MOD is the max PPO2 limit which should not be exceeded.

Regards Gary

[Mal Bridgeman]

Now you have all the sensible answers to your question.....I would suggest MOD is the Maximum operating depth, whereas a TOD is what Scottish people leave in the loo
Mal

[ardhill]

Originally Posted by garygee

TOD or target opperating depth is the depth at which you plan your PPO2 at, maybe you plan a PPO2 of 1.3 at depth X

But surely this doesn't really matter with Nitrox? Yes, it matters how deep you can go on a mix eg Maximum Operating Depth at 1.4 PPO2, but I can happily use Nitrox 30 or 40 at 6 metres, yes they will go further, but what point is there in setting a PPO2 'target' shallower than your maximum depth? As long as you don't exceed your max, then surely there isn't a problem.

I could understand it if we were talking about trimix, were we had a lean O2 mix. Then you wouldn't want to breathing that till you reached a 'target' depth, or whatever it is 'officially' called.

I though it was all confusing enough with all those DUI, DIR, DCI, DCS's now we have MOD and TOD's

[ardhill]

Originally Posted by Mal Bridgeman

Now you have all the sensible answers to your question.....I would suggest MOD is the Maximum operating depth, whereas a TOD is what Scottish people leave in the loo
Mal

Nah mate, you are getting it confused with a Scottish TODdy
.