Hi there,
I was recently involved in a discussion about the subject and within the group there was no definitive answer achieved. The issue is theoretical and relates to the partial pressure of gasses.
I'll try and summarise the key issues and assumptions.
1. For this hypothetical, disregard lung over expansion injuries, they are understood and agreed to be an issue that applies in reality.
2. The accepted mod of 21% Air is between 56.7m (ppO2=1.4) and 66.2m (ppO2=1.6ata).
3. A free-diver does not experience the negative effects of partial pressure of O2 because the air is breathed at 1 ata and at that point there are no negative effects.
Question:
A SCUBA diver using 21% (normal) air descended to 56m, took a breath of air and then holding his breath (contravening the basic rules, yes) descended to 100m and then ascended back to 56m without breathing from the tank below 56m.
- Would this diver be subject to the negative effects of the increased partial pressure of O2?
- Would this diver have had a deco requirement in addition to the 56m ?
This is a theoretical question and does not refer to the hero who bounce dives to 100m with a 50/50 risk of success.
Your thoughts?
Regards
Richard (Riger)
I was recently involved in a discussion about the subject and within the group there was no definitive answer achieved. The issue is theoretical and relates to the partial pressure of gasses.
I'll try and summarise the key issues and assumptions.
1. For this hypothetical, disregard lung over expansion injuries, they are understood and agreed to be an issue that applies in reality.
2. The accepted mod of 21% Air is between 56.7m (ppO2=1.4) and 66.2m (ppO2=1.6ata).
3. A free-diver does not experience the negative effects of partial pressure of O2 because the air is breathed at 1 ata and at that point there are no negative effects.
Question:
A SCUBA diver using 21% (normal) air descended to 56m, took a breath of air and then holding his breath (contravening the basic rules, yes) descended to 100m and then ascended back to 56m without breathing from the tank below 56m.
- Would this diver be subject to the negative effects of the increased partial pressure of O2?
- Would this diver have had a deco requirement in addition to the 56m ?
This is a theoretical question and does not refer to the hero who bounce dives to 100m with a 50/50 risk of success.
Your thoughts?
Regards
Richard (Riger)