bobbysocks
Chief Master Sergeant
actually I thought that contraption in the first post was like the "cone of silence" in Get Smart.....
Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
They were exactly coincidental, that is the scandal. The last few times I flew on long flights I felt terrible at the end of the flight. I have never said halting smoking on aircraft made matters worse but the airlines use of it to reduce air quality/refreshment rates and Oxygen levels did and still does.
The effects of drinking alcohol on long haul flights are well known, occasionally people go berserk, so they are severely restricting alcohol on flights (not a bad idea in my book). However there is another effect, people become very very emotional watching even the most placid of movies, flying a long haul flight tests out your response to low oxygen levels at low air pressure and with some it can be fatal.
How do they reduce oxygen?
They are decreasing the cabin altitude (787 is down to 6000', vs. 8000' for most current airliners) which has the effect of increasing the oxygen.
Please don't tell me you've fallen for the old conspiracy theory that airlines have reduced the oxygen levels to somehow save money.
GregP
Major
Pressure and Oxygen content are not the same thing, gumbyk.
When you breathe in the air and exhale, you have used some of the Oxygen. Eventually it will run out and you pass out and eventually die as you use up the Oxygen. That's how miners in a cave-in expire, by using up the Oxygen. The new planes simply let in less fresh air and thereby decrease drag. Taking in and expelling internal atmosphere produces drag and costs money.
Air pressure at sea level is about 14.7 pound per square inch. I can easily show you hydrogen at that pressure and let you breathe it. Your voice will change and you will be momentarily unaffected. If you continue to breathe it you will pass out and eventually die from lack of Oxygen.
When you breathe in the air and exhale, you have used some of the Oxygen. Eventually it will run out and you pass out and eventually die as you use up the Oxygen. That's how miners in a cave-in expire, by using up the Oxygen. The new planes simply let in less fresh air and thereby decrease drag. Taking in and expelling internal atmosphere produces drag and costs money.
Air pressure at sea level is about 14.7 pound per square inch. I can easily show you hydrogen at that pressure and let you breathe it. Your voice will change and you will be momentarily unaffected. If you continue to breathe it you will pass out and eventually die from lack of Oxygen.
Didn't Adolf Galland have ashtrays installed in his planes?
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
He had a cigar lighter installed (like found in automobiles)
parsifal
Colonel
How someone could smoke a cigar in the confines of an Me 109 cockpit is just beyond me
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Bf109 have a vent that's not easily seen unless it's open. From inside the cockpit, it was located just above the trim/flap wheel.
I'm aware of how the partial pressure of oxygen works.
Have a read of FAR 25.831 (I think, I'm working from memory) where it dictates the amount of ventilation air that is to be provided per person per minute (0.55lb/person/min).
It's not about moderation. There is no safe level of exposure to cigarette smoke apart from ZERO.
There are other potential causes of pulmonary problems but the studies carried out around the world, including those I quoted from in the UK and US, go to great lengths to calculate the disease caused by smoking and passive/second hand smoking and isolating that from other causes.
Cheers
Steve
GregP
Major
Since you are aware of that, gumbyk, your question makes less sense to me than it did before.
Pressurization is just pressurization. The Oxygen content is unrelated to the cabin pressure in a pressurized aircraft.
So, I'll just say that the new generation of airliners controls the amount of outside air introduced to a much lower level than previous generations of airliners did, and let it go at that. There is half as much Oxygen at 20,000 feet as there is at sea level. Since airliners typically cruise in the upper twenties to low to mid thirties, that means when they DO allow outside air in, the Oxygen content is not much, less than 1/3 of what we breather at sea level. It results in a much lower level of Oxygen content than normal, but is technically legal.
Pressurization is just pressurization. The Oxygen content is unrelated to the cabin pressure in a pressurized aircraft.
So, I'll just say that the new generation of airliners controls the amount of outside air introduced to a much lower level than previous generations of airliners did, and let it go at that. There is half as much Oxygen at 20,000 feet as there is at sea level. Since airliners typically cruise in the upper twenties to low to mid thirties, that means when they DO allow outside air in, the Oxygen content is not much, less than 1/3 of what we breather at sea level. It results in a much lower level of Oxygen content than normal, but is technically legal.
O.K. yes, there is 1/3 the amount of ALL gasses at 20k, but the proportion of oxygen doesn't change, it still makes up 21% of the atmosphere., pressurise the cabin to sea level, and you're back to the sea level amount of oxygen available.
How do the airlines reduce the amount of oxygen? There isn't less oxygen in the atmosphere - there is less atmosphere. pressurise the aircraft, and you're back to having more atmosphere, and more oxygen.
How do the airlines reduce the amount of oxygen? There isn't less oxygen in the atmosphere - there is less atmosphere. pressurise the aircraft, and you're back to having more atmosphere, and more oxygen.
GregP
Major
At 20,000 feet, NOTHING is the same as at sea level except the proportions. Unless they supplement the air with on-board Oxygen, there is simply not enough there. Now I don't want to pretend I'm a pressurization expert, but every single thing I read about it says the new generation of planes have lower Oxygen levels than the older generation did. So either they pressurize to a higher altitude or they recirculate the on-board air and only let in a little from outside.
My reading tells me they recirculate more and let in less fresh air, meaning the Oxygen level drops from the normal percentage to less. I wouldn't be at all surprised to see 16% Oxygen on a 777 approaching one side of the Atlantic or the other.
My reading tells me they recirculate more and let in less fresh air, meaning the Oxygen level drops from the normal percentage to less. I wouldn't be at all surprised to see 16% Oxygen on a 777 approaching one side of the Atlantic or the other.
O.K. quick primer on how pressurisation works:
Air is taken form outside the aircraft, pressurised by the engines, and pumped into the fuselage, the pressurisation is controlled by adjusting the amount of air that flows out of the fuselage, via the outflow valves. There is no control on what goes in (there may be something to prevent over-pressurisation in the event of outflow valve failure, but I'm not sure).
So, short of having some means of stripping the oxygen from the air (sounds about as convincing as chemtrails to me), each person is being supplied with 0.12lbs of oxygen per minute (0.55 lbs, which is the minimum airflow allowed under FAR25 *21%) which is more than enough.
The amount of fresh air that they let in is regulated, so unless manufacturers have some sort of conspiracy going with the FAA, then I doubt there is any less oxygen.
More likely is that as aircraft have cruised higher, then there is less moisture in the atmosphere, and dehydration is the real cause for headaches, etc that get reported.
FWIW, I doubt you'd even notice a reduction to 16% oxygen if you're fit and healthy.
The truth about cabin air
Please don't tell me you're quoting this among your reading. They're known for their pseudo-scientific woo.
Last edited:
GregP
Major
You figure it out. It's not a subject I'm willing to put much more time into, but I'd hazard that almost everyone in here knows the basics you laid out above, including me.
I have never seen your second link before since it is not something that tweaks my interest much. But, Oxygen levels have dropped in recent airliners. Ask Boeing.
Cheers.
I have never seen your second link before since it is not something that tweaks my interest much. But, Oxygen levels have dropped in recent airliners. Ask Boeing.
Cheers.
I had a look, but I don't have any contact in Boeing to back up your claim.
Have you got a reference for your reading so I can educate myself? I've given you the FAR reference for how much air (and thus oxygen) is to be supplied per person per minute, could you please do the courtesy of giving me your references?
Have you got a reference for your reading so I can educate myself? I've given you the FAR reference for how much air (and thus oxygen) is to be supplied per person per minute, could you please do the courtesy of giving me your references?
GregP
Major
Here's a quote from the regulations.
Section 25.83 1 (a) specifies that the ventilation system must be designed to provide a
minimum of 0.55 pounds of fresh air per minute per person (10 cubic feet per minute of air at 8,000
feet pressure altitude and at cabin temperature of 75" F.) for normal operations. If the airplane
incorporates a recirculation system, the required fresh air may be mixed with filtered, recirculated air.
A larger amount of fresh air may be required due to secondary considerations, such as equipment
cooling, window or windshield defogging, control of smoke or toxic fumes, or smoke evacuation.
Increased fresh air flow may also be needed in some instances to compensate for high ambient
temperatures and humidity. The mass flow following probable failures is addressed in paragraph 5.e
of this AC.
I bolded the part that should tell you why the Oxygen level is lower.
Section 25.83 1 (a) specifies that the ventilation system must be designed to provide a
minimum of 0.55 pounds of fresh air per minute per person (10 cubic feet per minute of air at 8,000
feet pressure altitude and at cabin temperature of 75" F.) for normal operations. If the airplane
incorporates a recirculation system, the required fresh air may be mixed with filtered, recirculated air.
A larger amount of fresh air may be required due to secondary considerations, such as equipment
cooling, window or windshield defogging, control of smoke or toxic fumes, or smoke evacuation.
Increased fresh air flow may also be needed in some instances to compensate for high ambient
temperatures and humidity. The mass flow following probable failures is addressed in paragraph 5.e
of this AC.
I bolded the part that should tell you why the Oxygen level is lower.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
GregP
Major
Amen to desaturation. I knew a pilot who went up to fly some aerobatics, lit a cigarette at 10,000 feet and woke up in a more or less level circle at 5,000 feet sometime later (in a Citabria). He never smoked in a light aircraft again.
I rode competitively on off-road motorcycles in and around Arizona for about 20 years, and we noticed a big difference at 5,000+ feet. Not when sitting still, but when exerting yourself on a motorcycle. We were in decent shape physically. I've seen a few folks not in good shape who just lost all their energy in Flagstaff or anywhere up on the Mogollon Rim.
I could have my doubts about the cabin level in some aircraft since I am quite familiar with the feeling at elevated altitude. Let me say it this way. If I am not doing any exercising, I don't really notice 5,000 feet. If I noticed in in a plane, then I would doubt I am at 5,000 feet cabin altitude. To date, I have not noticed altitude in a pressurized airliner, but know a few who have noticed it a bit. I didn't even notice it in a turbocharged Mooney at 16,000 feet either, but we had Oxygen masks on at the time and I saw no reason to attempt to make the Mooney an altitude test chamber, so I didn't take it off to see how long I'd remain unaffected.
I've also never flown in a 787 or one newer airliners that supposedly cheat the air a bit. They are supposed to use more recirculation than older jets do. The incoming air remains at 21% Oxygen, even if less Oxygen is there due to altitude. But if you mix it with air that has been breathed in and out and recirculated for an hour, the resulting mixture will not be at 21%. Basic chemistry of mixtures. All mixtures have a concentration between the lower one and the upper one when you mix to gasses or liquids.
My sister is one of the susceptible people. She would get sick a few days from flying about 40% of the time when she was traveling for work (attorney). Usually it was a cold or the like. Now that she is retired, she doesn't fly (on commercial airliners) unless distance dictates it that way. She has no issue with flying in a small plane or small bisjet, just commercial, and her issue is one of statistics of catching something on the flight, not any fear of flying.
I rode competitively on off-road motorcycles in and around Arizona for about 20 years, and we noticed a big difference at 5,000+ feet. Not when sitting still, but when exerting yourself on a motorcycle. We were in decent shape physically. I've seen a few folks not in good shape who just lost all their energy in Flagstaff or anywhere up on the Mogollon Rim.
I could have my doubts about the cabin level in some aircraft since I am quite familiar with the feeling at elevated altitude. Let me say it this way. If I am not doing any exercising, I don't really notice 5,000 feet. If I noticed in in a plane, then I would doubt I am at 5,000 feet cabin altitude. To date, I have not noticed altitude in a pressurized airliner, but know a few who have noticed it a bit. I didn't even notice it in a turbocharged Mooney at 16,000 feet either, but we had Oxygen masks on at the time and I saw no reason to attempt to make the Mooney an altitude test chamber, so I didn't take it off to see how long I'd remain unaffected.
I've also never flown in a 787 or one newer airliners that supposedly cheat the air a bit. They are supposed to use more recirculation than older jets do. The incoming air remains at 21% Oxygen, even if less Oxygen is there due to altitude. But if you mix it with air that has been breathed in and out and recirculated for an hour, the resulting mixture will not be at 21%. Basic chemistry of mixtures. All mixtures have a concentration between the lower one and the upper one when you mix to gasses or liquids.
My sister is one of the susceptible people. She would get sick a few days from flying about 40% of the time when she was traveling for work (attorney). Usually it was a cold or the like. Now that she is retired, she doesn't fly (on commercial airliners) unless distance dictates it that way. She has no issue with flying in a small plane or small bisjet, just commercial, and her issue is one of statistics of catching something on the flight, not any fear of flying.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
A few years back, I rode in an Alitalia 777 to and from Europe, we took the Polar route and were anywhere between 39 and 50 thousand for the most part.
The air quality was fine and the cabin temps were nice. Actually, my only complaint with the airline, was giving me only 9 minutes to get from one end of the airport (Rome) to the other during a transfer, on my trip home. Needless to say, I didn't make it (they had just closed the gate) so I ended up getting home a day late.
Now the air quality at the Rome airport was horrible...it was warm and brutally humid.
The air quality was fine and the cabin temps were nice. Actually, my only complaint with the airline, was giving me only 9 minutes to get from one end of the airport (Rome) to the other during a transfer, on my trip home. Needless to say, I didn't make it (they had just closed the gate) so I ended up getting home a day late.
Now the air quality at the Rome airport was horrible...it was warm and brutally humid.
