Commercial jet air we breath

[Eastwest]

I was not trying to be a jerk , all this information is very interesting and still wonder if they scrub the co2 . The link does not mention it .

 

[jborg]

There is no scrubbing. About 200-250 litres of air per minute per passenger is replaced from the outside. Supposedly this results in all cabin air being replaced roughly every three minutes (precise details being aircraft-specific etc obviously). (I doubt they tune the air replacement rate based on the number of actual passengers for each flight, rather I would expect it to be based on the max capacity.)

 

[stepfen]

Supposedly this results in all cabin air being replaced roughly every three minutes (precise details being aircraft-specific etc obviously)

Hmmm, out of curiosity, are O2/CO2/CO etc levels actually being measured or it is assumed that with so high replacement rates air quality is always good???

Where is @DandyDon when you need him

 

[Canajan]

The pressurization computer regulates the cabin altitude on a programmed schedule. The outflow valve is commanded by the press comp, and yup about every few minutes technically the complete cabin has been exchanged.
There is no measuring beyond temperatures, pressure and aircraft like the 787 measure humidity.
The air quality is decent I would say, but have never measured it.
The 787 is newer and the air exchange takes longer as the aircraft was made for efficiency.

 

[BRT]

The air you breath will always be 21% oxygen

But the partial pressure will not be.

 

[rjack321]

Hmmm, out of curiosity, are O2/CO2/CO etc levels actually being measured or it is assumed that with so high replacement rates air quality is always good???

Where is @DandyDon when you need him

why would you even need to measure? what would be the point? its not like you can do anything about a "high co2" measurement at 30,000ft

 

[broncobowsher]

You are thinking aircraft are way more complex than they really are.
If you knew how crude they really are you probably wouldn't fly on them.
Outside air is compressed, blown in, and (controlled) leaked out just as fast.

Friend of mine was describing when there was a flaw in a line of computer code, the fix wasn't to fix the code as that would require a whole new certification. But install hardware (put in a resistor into the wiring) as the fix. That was much easier to get approved than just correcting the coding in the computer. Engineering wise, more complex. Paperwork and costwise, easier.

When I had to do business trips to Mexico I enjoyed getting to altitude. About the time we leveled off was the time my head cleared up from the air pollution I had been sucking in for the past week.

 

[Eastwest]

The compressed air we breath and diving at 5 atmospheres becomes problematic , so the reply given that the cabin pressure is maintained at 9 percent equivalent to 8000 feet altitude and sucking air into the cabin at 30,000 feet keeping O2 at 21 percent that equation may be missing something .

 

[Angelo Farina]

But the partial pressure will not be.

The partial pressure will be 21% of the total pressure.
At 8000 ft the total pressure is 75262 Pa (0.75 bar).
So, the pp of O2 is 0.21 bar at sea level, and 0.152 bar at 8000 ft (inside the aircraft cabin).

 

[BRT]

The partial pressure will be 21% of the total pressure.
At 8000 ft the total pressure is 75262 Pa (0.75 bar).
So, the pp of O2 is 0.21 bar at sea level, and 0.152 bar at 8000 ft (inside the aircraft cabin).

It will indeed be 21% of the total pressure. And at 33 feet the oxygen is still 21% of the total pressure. Which doesn't help us stay alive at high elevations or avoid oxygen toxicity at deep depths.