Time to Desaturation?

[roakey]

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. "

How redundant. I've always found IANTD manuals very wordy for the amount of information they convey, this is a great example.

Roak

 

[serambin]

How redundant. I've always found IANTD manuals very wordy for the amount of information they convey, this is a great example.

Roak

Personally I'm redoubling my efforts to understand the Genesis manual.

Stan

 

[chris123]

Hi,
I know this is an old discussion, but my question relates directly to it:

I have been diving over the last 3 days, with 3 dives the first day, 3 dives yesterday and 1 dive today early morning.
Initial flight for tomorrow has been cancelled and the dive company re-booked me to a flight TONIGHT, giving me 13 hours surface interval.

I had two dive computers with me all time. One computer (Suunto Ocean) shows me a 12 hour no flight limit, suggesting it should be fine. The other (older) computer shows the standard 24 hours, but also shows a desaturation time of 10 hours.

From my understanding, Suunto no fly time is based on desaturation time but minimum 12 hours.

Just super surprised that
1. Suunto shows 12h no fly time after multiple days of diving.
2. Dive company re-booked on flight after 13hr surface interval, arguing that it's a short domestic flight.

PS: Last days were on air, last dive yesterday was shallow (11m average) and today's dive was with 32% nitrox but computer on air profile.

 

[tursiops]

today's dive was with 32% nitrox but computer on air profile.

Why do you do this? Now you do not know your N2 or O2 status.

 

[chris123]

Why do you do this? Now you do not know your N2 or O2 status.

Diving with nitrox and setting to air is considered more cautious.

In any case, second computer was set to nitrox but also shows desat time of few hours before flight time.

 

[chris123]

Diving with nitrox and setting to air is considered more cautious.

Dive computer will calculate with a higher N2 level of 21% instead of 32%, i.e. calculated N2 saturation is higher than actual saturation. This way is no problem, other way is more of an issue, based on my understanding.
From what I learned, O2 saturation shouldn't be an issue, rather N2 saturation I should be worried about when flying (13hr) after diving

 

[chris123]

Anyway my main question is, regardless of air and nitrox, how come Suunto shows 12hr no flight after multiple days of diving?

 

[tursiops]

Diving with nitrox and setting to air is considered more cautious.

Maybe 20 years ago. No reason to lie to your computer.

 

[chris123]

Maybe 20 years ago. No reason to lie to your computer.

Thanks. Very helpful.

 

[JMarc]

Diving with nitrox and setting to air is considered more cautious.

If you want to increase the safety factor, there are settings designed for that. Lying about gas composition or altitude is no more needed than fudging with depth and time (which was used with tables, I never saw a computer allowing that).