Quiz - Physics - Partial Pressure of Carbon Monoxide

[Pedro Burrito]

This question is in honor of @DandyDon - the CO king!

A scuba tank containing 1.5% carbon monoxide at the surface is taken down to 40 meters/132 feet. If a diver were to breathe from that tank at this depth, it would have the same effect as breathing ____ percent of carbon monoxide at the surface.

a. 1.5
b. 6.0
c. 7.5
d. 3.0



I will post a daily question from my exams to help newer divers and to encourage more experienced divers to interact gracefully and helpfully with the newer divers.

Reminder - this is a post in the Basic Forum and it is a green zone. Please be nice and on topic.

Thank you for your patience while we try to give people something to discuss other than Covid-19 and/or Politics. I will post the answer covered by the spoiler tag later today.

 

[Ukmc]

This was the exact question on my SSI science of diving

 

[DandyDon]

He wouldn't be breathing long enough to matter.

 

[saxman242]

If we go off the PADI study notes, anything over 1.5% means unconsciousness with a near 0 exposure time, so at depth, the effect would be the same as 1.5%.


Now, I'm guessing you're actually looking for a partial pressure based answer and not a physiology based answer.

 

[DandyDon]

If we go off the PADI study notes, anything over 1.5% means unconsciousness with a near 0 exposure time, so at depth, the effect would be the same as 1.5%.

It's been 20 years since I took Padi's OW course, but I don't think it was mentioned at all then. It is now? I bet it's lip service at best. Rule 1 is it doesn't take much, and Rule 2 is you never know unless you test every tank.

1.5% = 15,000 ppm so for most (people and reactions vary) it'd take maybe two or three breaths to knock you out, a few minutes to die. It can get confusing trying to compare percentage points (parts per hundred) to parts per million and the comma can too easily be displaced. See Percent (%) to ppm conversion calculator | number conversion
and Carbon monoxide poisoning - Wikipedia

 

[saxman242]

It's been 20 years since I took Padi's OW course,

It's been longer since I took it, so I'm not sure. The reference material I was speaking of was actually from a padi IDC study pack I came across.

 

[saxman242]

PADI IDC Study Notes - Carbon Monoxide Poisoning, Oxygen Toxicity and Nitrogen Narcosis - IDC Bali Internships

 

[DandyDon]

Ok, well, I didn't answer Pedro's question, so that's still open ground.

 

[Ukmc]

It is very interesting, as the question really doesn’t test anything in regard to carbon monoxide effects or lethal levels. It tests Henry’s law and knowledge of bars per 10fsw as well as remembering to add atmospheric pressure. It could have been any gas and the calculation would be the same. However, the testers wanted to give a nod to carbon monoxide, I assume to raise awareness? There was only one other question on the entire Science of Diving test related to carbon monoxide - what are the avenues of how CO can get into the tank - also I assume to raise awareness that it can happen and present a danger. There were no questions on physiology or dose related injury.

 

[johndiver999]

Wow, that is a really bad test question. Makes zero sense.