What is the 130 rule?

[nimoh]

I believe that the equation should read:

Max Depth + Bottom Time < 130 = No Decompression Diving on 32%

i.e. if the sum of max depth and bottom time is less than 130, you do not have deco obligations. If it is greater than 130, you might have deco obligations.

As for the example,

70' + 45mins = 115.

115 is less than 130, so it is a no decompression dive.

 

[mathauck0814]

I believe that the equation should read:

Max Depth + Bottom Time < 130 = No Decompression Diving on 32%

i.e. if the sum of max depth and bottom time is less than 130, you do not have deco obligations. If it is greater than 130, you might have deco obligations.

As for the example,

70' + 45mins = 115.

115 is less than 130, so it is a no decompression dive.

Right, sorry. Brainfart. You get the idea now though, right?

 

[vcblklion]

I got it...Thanks

 

[Mr Carcharodon]

A lot of people use average depth instead of max depth. But then a "sensible" profile is assumed. 120 rule is the same thing for air.

 

[The Chairman]

I don't know of anyone who uses either rule as anything but a backup plan should your PDC crap out. Hopefully you were keeping track up to the point it did.

 

[PfcAJ]

Ya you do! Me!

 

[Searcaigh]

I believe that the equation should read:

Max Depth + Bottom Time < 130 = No Decompression Diving on 32%

i.e. if the sum of max depth and bottom time is less than 130, you do not have deco obligations. If it is greater than 130, you might have deco obligations.

As for the example,

70' + 45mins = 115.

115 is less than 130, so it is a no decompression dive.

Obviously does not work for metric

130 for me is time to go back to work after lunch

 

[Tortuga68]

In metric it's 45 (for air)

Works ok as a rule of thumb for deeper depths, as someone pointed out it cuts the dive a bit short at shallower depths... but if you're <=18m you don't really need to worry about NDL anyway

 

[PfcAJ]

I believe for Nitrox32 it's "30m for 30mins". Every 3m shallower gets you 10 more minutes of NDL time.

 

[DA Aquamaster]

I get a PO2 =1.58 for EAN 32 @ 130 feet. . . A little 'sporty' for me. . .

I'm just quoting the NOAA numbers, I'm not saying I agree with them.

When I first took a Nitrox class in the 90's "Nitrox I" (32%) and "Nitrox II" (36%) were the norm and a PPO2 of 1.6 was considered acceptable for the working portion of the dive. That PPO2 is still used for deco now, but it's been scaled back to 1.4 by most agencies for the working portion of the dive. I prefer to keep it down around 1.3 and I know some divers who shoot for 1.2.

I regard 100' as about the limit for 32% for the working portion of the dive, and I prefer to use 30% on 110 ft dives.

What that means however is that the 130 rule actually works pretty well if you restrict your diving on 32% to no more than 100', and essentially stay with the numbers in blue as you'll also be limiting the max PPO2 to 1.3 at 100'.