Time to Desaturation?

[serambin]

My new Geneses React Pro offers a 'Time to desaturation' count down on the 'Time to Fly' screen. Can anyone tell me about this number? For example-

1. Is this number total desaturation of Nitrogen from the body?

2. How is it best used after the dive?

3. Is it additional information for flight time or used for something else?

Thanks,

Stan

 

[CIBDiving]

My new Geneses React Pro offers a 'Time to desaturation' count down on the 'Time to Fly' screen. Can anyone tell me about this number?

Since the computer waits 2 hours Before entering this mode, The No fly time is 22 hours or less (22 +2 for a 24 hour no fly), The Sat time is 10 hours or less(10 +2 for a 12 hour Sat time).

The 'Sat' time is not N2 - It's O2! .
If you're not diving nitrox Ignore it. If you're nitrox qualified then Shame on you! - it's your O2 clock reset time.

From the IANTD synopsis of the basic nitrox course -
" If a series of dives in a 24 hour period reaches the Daily Limits, then a 12 hour surface interval breathing normoxic air must be taken before diving again. "

 

[serambin]

Since the computer waits 2 hours Before entering this mode, The No fly time is 22 hours or less (22 +2 for a 24 hour no fly), The Sat time is 10 hours or less(10 +2 for a 12 hour Sat time).

The 'Sat' time is not N2 - It's O2! .
If you're not diving nitrox Ignore it. If you're nitrox qualified then Shame on you! - it's your O2 clock reset time.

From the IANTD synopsis of the basic nitrox course -
" If a series of dives in a 24 hour period reaches the Daily Limits, then a 12 hour surface interval breathing normoxic air must be taken before diving again. "

I'm not Nitrox certified yet, but it is my next course. Thanks for the info.

Stan

 

[WellBelowH2O]

Since the computer waits 2 hours Before entering this mode, The No fly time is 22 hours or less (22 +2 for a 24 hour no fly), The Sat time is 10 hours or less(10 +2 for a 12 hour Sat time).

The 'Sat' time is not N2 - It's O2! .
If you're not diving nitrox Ignore it. If you're nitrox qualified then Shame on you! - it's your O2 clock reset time.

From the IANTD synopsis of the basic nitrox course -
" If a series of dives in a 24 hour period reaches the Daily Limits, then a 12 hour surface interval breathing normoxic air must be taken before diving again. "

Sat time is related to N2, not O2. Time to Desaturation is the computer calculating the amount of time you'll need to completely offgas nitrogen--a theoretical measure of when you'll be free of excess nitrogen vs. Time to Fly which is simply a 24 hour countdown from the conclusion of your last dive. Of course, it is only an estimate as each individual may offgas at different rates, so continue to use the Time to Fly number before you get into a plane.

 

[Charlie99]

Since the computer waits 2 hours Before entering this mode, The No fly time is 22 hours or less (22 +2 for a 24 hour no fly), The Sat time is 10 hours or less(10 +2 for a 12 hour Sat time).

The 'Sat' time is not N2 - It's O2! .
If you're not diving nitrox Ignore it. If you're nitrox qualified then Shame on you! - it's your O2 clock reset time.

The Genesis React Manual doesn't agree with you. It has nothing to do with O2.

http://www.genesisscuba.com/manuals/REACT_PRO_Owners_Manual.pdf , see page 43.

The Desat time is the calculated times for tissue desaturation of N2 at sealevel. If the calulated time is greater than 9:59, then the display will show 9:++ until it becomes less than 9:59.

It looks pretty similar to the desat countdown on my Oceanic Data Plus, probably because both the Genesis and Oceanic are made by Pelagic Pressure Systems. Quite frequently the desat time on my computer is greater than 12 hours, and if I've been doing long shallow dives on air, or long medium depth dives on nitrox, it will exceed 24 hours --- i.e. still have a desat time of 3 or 4 hours when the 24 hour time-to-fly time counts down to zero.

Unfortunately, the manual doesn't say specifically what compartment loading they use as the cutoff point to call it "desaturated".

 

[Charlie99]

1. Is this number total desaturation of Nitrogen from the body?

2. How is it best used after the dive?

3. Is it additional information for flight time or used for something else?

1. Not exactly "total" desaturation. Exponential functions never go to zero, they gets get closer and closer. But close enough to total desat that your computers is willing to just throw away the info and ignore it.

2. It's not easy to use, since for any signficant saturation level, it just reads 9:++ after the dive.

3. I won't fly until desat goes to zero.

It won't go beyond 24 hours unless you've been diving pretty heavily. For example, a couple weeks ago, the maximum desat time was 25:42, and that was after 235 minutes of bottom time, mostly at 60' on EAN36 the previous day. The day before that, two dives of 1:02 and 1:01 on EAN36 on the inside ledge of 3rd reef off of Boynton Beach, FL (about 60') took the desat up to 22:02.

For comparison, the first two dives of the trip were on air, on the shallower 2nd reef off of Hillsboro. 42' max, only about 35' average. Two dives of 0:58 and 1:13 left the computer with a desat time of 20:20. (Because of the limited 10 hour max display, you have to look at the computer the next morning to find out what it is from the previous day).

 

[serambin]

1. Not exactly "total" desaturation. Exponential functions never go to zero, they gets get closer and closer. But close enough to total desat that your computers is willing to just throw away the info and ignore it.

2. It's not easy to use, since for any signficant saturation level, it just reads 9:++ after the dive.

3. I won't fly until desat goes to zero.

It won't go beyond 24 hours unless you've been diving pretty heavily. For example, a couple weeks ago, the maximum desat time was 25:42, and that was after 235 minutes of bottom time, mostly at 60' on EAN36 the previous day. The day before that, two dives of 1:02 and 1:01 on EAN36 on the inside ledge of 3rd reef off of Boynton Beach, FL (about 60') took the desat up to 22:02.

For comparison, the first two dives of the trip were on air, on the shallower 2nd reef off of Hillsboro. 42' max, only about 35' average. Two dives of 0:58 and 1:13 left the computer with a desat time of 20:20. (Because of the limited 10 hour max display, you have to look at the computer the next morning to find out what it is from the previous day).

Thanks - For example while in the Keys over the last week and diving each day, on Wednesday after my last dive, I showed 7:56 as the desaturation time. Most of the diving was in 25' or less with only one :59 minute dive at 60'. Does the 7:56 present a running total of Nitrogen for the previous 4 days or just the saturation after the last series of dives? (The above mentioned manual is pretty worthless on details)

Thanks again,

Stan

 

[WellBelowH2O]

Thanks - For example while in the Keys over the last week and diving each day, on Wednesday after my last dive, I showed 7:56 as the desaturation time. Most of the diving was in 25' or less with only one :59 minute dive at 60'. Does the 7:56 present a running total of Nitrogen for the previous 4 days or just the saturation after the last series of dives? (The above mentioned manual is pretty worthless on details)

The time to desaturation will represent the amount of time until all excess nitrogen has been offgassed from any dives that you've been doing. So if you had a couple of dives and your computer never reached 0 for desaturation, the computer would take in that residual nitrogen into account when you went down on your next dive, etc. and add it into the nitrogen you loaded on your most recent dive.

If you had a SIT in which you were completely offgassed (according to your computer) when you started your next dive, the counter would have been reset and only that dive you just did would start the saturation clock.

 

[redacted]

It looks pretty similar to the desat countdown on my Oceanic Data Plus, probably because both the Genesis and Oceanic are made by Pelagic Pressure Systems. Quite frequently the desat time on my computer is greater than 12 hours, and if I've been doing long shallow dives on air, or long medium depth dives on nitrox, it will exceed 24 hours --- i.e. still have a desat time of 3 or 4 hours when the 24 hour time-to-fly time counts down to zero.

I believe you are referring to the DataPlus 2. I don't believe the DataPlus provides desaturation times.

 

[Charlie99]

I believe you are referring to the DataPlus 2. I don't believe the DataPlus provides desaturation times.

Hmmmm. Let me count the buttons. 1....2. Yep, a DataPlus 2.

The 2 buttons really do make for a much nicer user interface than the 1 button operation of the older DataPlus computer that spends most of it's life in my save-a-dive kit.