Excel Formula Spreadsheet

jdicediver · 8th February 2007, 20:12

I have attached an excel spreadsheet (.zip) which has some handy formulas in it. Lets see if we can come up with a comprehensive version for use. Please check that these formulas are correct and update with new, if you have. Input requested, with new version to be reposted by updatee.

**Scott** · 8th February 2007, 21:10

I don't have any reference material.. but I was under the impression that Minimum Operating Depth was the depth at which a hypoxic mix diluent will no longer support life, which is approximately .10 pO2

jdicediver · 9th February 2007, 16:53

Quote: (Originally Posted by Scott)

I don't have any reference material.. but I was under the impression that Minimum Operating Depth was the depth at which a hypoxic mix diluent will no longer support life, which is approximately .10 pO2

<Obtained from an article in tacticaldiving.com>
We operate at peak performance at a 24% oxygen level and at sea level on earth, the air consists of 21% oxygen. Most people start experiencing problems when the oxygen level goes below 17% which for instance mountaineers experiences on high altitudes. When the oxygen level falls below 8% most people will go unconscious.

Examining our oxygen dependency more closely reveals that what we really need is an enough amount of oxygen molecules. That means that if we increase the pressure four times, like diving on 30 meters depth, we can survive on a quarter of the oxygen level or 5% oxygen in the breathing gas. There is a special name for the combination of pressure and oxygen percentage which is "oxygen partial pressure" or simply ppO2 for short. So 5% oxygen with 4 times the pressure would be expressed as a partial pressure of 0.20 bar (0.05 * 4).

It is however not only too low levels of oxygen that can be dangerous but also too high levels of oxygen. If someone would be exposed to a partial pressure of 3 bar (20 meters depth if someone breaths 100% oxygen) they would after a couple of minutes suffer severe body convulsions and go unconsciousness. The body of the victim would first become totally stiff for 30 to 60 seconds which is known as the tonic phase. After the tonic phase the victim will relax for 60 to 120 seconds and hyperventilate which is known as the clonic phase. If the diver is brought to the surface and treated he will most likely survive.

jdicediver · 9th February 2007, 16:54

Does anyone have any comments about the formulas in this spreadsheet? How is Minimum Operating Depth determined?

**Scott** · 9th February 2007, 17:33

Relationship : Pg/(Fg*Data)

Pg = Minimum Partial Pressure of Oxygen which will support life( or for safety's sake, consciousness)

Fg = Fraction of oxygen in the gas

Data = depth in atmospheres absolute

If when solving for Data, Data is 1.0 or less, the gas mix used will support life all the way to the surface..

For example: Using 10/70 trimix, PPO2 of .16 as minimum (for resting metabolism, .12 would be borderline function asleep, as per ANDI CCR manual for Meg)

Data = Pg/Fg
Data = .16ata O2/10% O2
Data = .16ata/.10
Data = 1.6ata
MinOD= 1.6ata

Dft = (Data - 1atm)*33ft
Dft = (1.6ata - 1atm)*33ft
Dft = .6atm*33ft
Dft = 19.8 ft
MinOD = 19.8 ft

Dm = (Data - 1atm)*10m
Dm = (1.6ata - 1atm)*10m
Dm = .6atm*10m
Dm = 6m
MinOD = 6m

jdicediver · 9th February 2007, 21:22

Here, the Minimum Operating Depth calculation has been corrected (hopefully) Can someone please verify the data calculations in this spreadsheet?

chunter · 9th February 2007, 21:32

I wouldn't have the minimum PPO2 any lower than 21%. Why would you intentionally push yourself into a hypoxic mix? If you were going to build this spreadsheet based on what a human can survive, why not push the MOD down to a 2.8 or higher? I would have the minimum at 0.21 and the maximum at 1.6.

Aloha,
Charlie

chunter · 9th February 2007, 21:37

I have attached a spreadsheet for SC rebreathers to calculate your inspired mix based on VO2 and Orifice size.

I make no claims that it is accurate, or that it should be used. Use it at your own risk!

Aloha,
Charlie

jdicediver · 13th February 2007, 23:02

Bigger, better, faster, quicker...would someone please check the accuracy?

8th February 2007, 21:10	#2 (permalink)
Scott Supporting Member Current Rebreather/s: Other CCR Other Rebreather/s: Megalodon Other CCR Join Date: Mar 2006 Location: Mendota, Virginia Posts: 181	Re: Excel Formula Spreadsheet I don't have any reference material.. but I was under the impression that Minimum Operating Depth was the depth at which a hypoxic mix diluent will no longer support life, which is approximately .10 pO2
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9th February 2007, 16:53	#3 (permalink)
jdicediver John Harcus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Calgary, Alberta Posts: 276	Re: Excel Formula Spreadsheet Quote: (Originally Posted by Scott) I don't have any reference material.. but I was under the impression that Minimum Operating Depth was the depth at which a hypoxic mix diluent will no longer support life, which is approximately .10 pO2 <Obtained from an article in tacticaldiving.com> We operate at peak performance at a 24% oxygen level and at sea level on earth, the air consists of 21% oxygen. Most people start experiencing problems when the oxygen level goes below 17% which for instance mountaineers experiences on high altitudes. When the oxygen level falls below 8% most people will go unconscious. Examining our oxygen dependency more closely reveals that what we really need is an enough amount of oxygen molecules. That means that if we increase the pressure four times, like diving on 30 meters depth, we can survive on a quarter of the oxygen level or 5% oxygen in the breathing gas. There is a special name for the combination of pressure and oxygen percentage which is "oxygen partial pressure" or simply ppO2 for short. So 5% oxygen with 4 times the pressure would be expressed as a partial pressure of 0.20 bar (0.05 * 4). It is however not only too low levels of oxygen that can be dangerous but also too high levels of oxygen. If someone would be exposed to a partial pressure of 3 bar (20 meters depth if someone breaths 100% oxygen) they would after a couple of minutes suffer severe body convulsions and go unconsciousness. The body of the victim would first become totally stiff for 30 to 60 seconds which is known as the tonic phase. After the tonic phase the victim will relax for 60 to 120 seconds and hyperventilate which is known as the clonic phase. If the diver is brought to the surface and treated he will most likely survive. __________________ Regards; "Some people shouldn't dive...others shouldn't even get wet".
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9th February 2007, 16:54	#4 (permalink)
jdicediver John Harcus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Calgary, Alberta Posts: 276	Re: Excel Formula Spreadsheet Does anyone have any comments about the formulas in this spreadsheet? How is Minimum Operating Depth determined? __________________ Regards; "Some people shouldn't dive...others shouldn't even get wet".
(Offline)

9th February 2007, 17:33	#5 (permalink)
Scott Supporting Member Current Rebreather/s: Other CCR Other Rebreather/s: Megalodon Other CCR Join Date: Mar 2006 Location: Mendota, Virginia Posts: 181	Re: Excel Formula Spreadsheet Relationship : Pg/(FgData) Pg = Minimum Partial Pressure of Oxygen which will support life( or for safety's sake, consciousness) Fg = Fraction of oxygen in the gas Data = depth in atmospheres absolute If when solving for Data, Data is 1.0 or less, the gas mix used will support life all the way to the surface.. For example: Using 10/70 trimix, PPO2 of .16 as minimum (for resting metabolism, .12 would be borderline function asleep, as per ANDI CCR manual for Meg) Data = Pg/Fg Data = .16ata O2/10% O2 Data = .16ata/.10 Data = 1.6ata MinOD= 1.6ata Dft = (Data - 1atm)33ft Dft = (1.6ata - 1atm)33ft Dft = .6atm33ft Dft = 19.8 ft MinOD = 19.8 ft Dm = (Data - 1atm)10m Dm = (1.6ata - 1atm)10m Dm = .6atm10m Dm = 6m MinOD = 6m Last edited by Scott : 9th February 2007 at 17:36.*
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9th February 2007, 21:32	#7 (permalink)
chunter I like diving Current Rebreather/s: Sport Kiss MK 15.X Other Rebreather/s: Inspiration Classic Inspiration Vision Evolution Classic Kiss Join Date: Jul 2006 Location: Honolulu Posts: 484	Re: Excel Formula Spreadsheet I wouldn't have the minimum PPO2 any lower than 21%. Why would you intentionally push yourself into a hypoxic mix? If you were going to build this spreadsheet based on what a human can survive, why not push the MOD down to a 2.8 or higher? I would have the minimum at 0.21 and the maximum at 1.6. Aloha, Charlie
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