RDP Table 3 Usage with Nitrox

[FPDocMatt]

2 questions regarding RDP table 3 usage with nitrox:

(1) Let's say you're planning 2 dives using the RDP, with different percentages of oxygen. For example, the first dive is with EAN32 and the second with EAN36. After the first dive, you use table 1 of the RDP for EAN32 to determine your pressure group. Then, after a surface interval, using table 2 of the EAN32 RDP, you figure out your after-surface-interval pressure group. At this point, to plan your second dive, do you use table 3 of the EAN32 RDP, or table 3 of the EAN36 RDP?

(2) In the above scenario, you are now using table 3 (of the appropriate RDP). At this point, when looking up your residual nitrogen time, do you use the depth of the second dive, or the depth of the first dive?

Thanks!

 

[Crowley]

(1) If you're planning it that way, then you should calculate your pressure group after surface interval using table 1 and 2 of the 32% RDP, then switch to table 3 of the 36% RDP to calculate your Adjusted NDL, residual nitrogen time and oxygen exposure.

(2) Using table 3 is the same amongst all versions of the RDP - it's based on the depth of your second dive - i.e.: After my surface interval I am in pressure group B. My second dive is to 16 metres. I must determine my limits at that depth given that I still have a bit of nitrogen left over from the first dive. You look at the box on table 3 where the depth of your second dive intersects with the PG after surface interval.

Hope that helps,

Cheers

C.

 

[FPDocMatt]

(1) If you're planning it that way, then you should calculate your pressure group after surface interval using table 1 and 2 of the 32% RDP, then switch to table 3 of the 36% RDP to calculate your Adjusted NDL, residual nitrogen time and oxygen exposure.



(2) Using table 3 is the same amongst all versions of the RDP - it's based on the depth of your second dive - i.e.: After my surface interval I am in pressure group B. My second dive is to 16 metres. I must determine my limits at that depth given that I still have a bit of nitrogen left over from the first dive. You look at the box on table 3 where the depth of your second dive intersects with the PG after surface interval.

Yep, that's the way I did it in my recent Nitrox class. I'm glad that I guessed right!

Thanks!

In reality, I'll just use my Mares Puck and leave the tables in my dive bag.

 

[RTee]

When using different EAN mixes, I bring everything to a common denominator...Air by calculating the EAD of each dive and plugging the numbers in the air table or eRDP