My experience of 12 years is that a healthy person will be functioning at FL120 but will feel really crap after an hour or two. At FL100 most will get a headache after say 2 hours and it will ruin their day.
Obviously there are exceptions and we can have many posts from such people. But why risk getting a distressed or ill passenger even if you think you are ok? Oxygen is so simple and cheap, on the scale of the costs we face everywhere.
In 2005 I was in a test group up to FL120. The results were eye opening to say the least. IIRC, some heart rates were approaching 120.
One problem in GA is that a lot of people eat chips and burgers and do no exercise. The one who could not read the altimeter was one of those.
Peter wrote:
My experience of 12 years is that a healthy person will be functioning at FL120 but will feel really crap after an hour or two. At FL100 most will get a headache after say 2 hours and it will ruin their day.
That sent me back some 20 years ago when I had a hankering for a Turbo Mooney… The seller offered a test trip from LFPN to LFMA – Marseille/Aix.
There was a howling Northerly up high so the owner decided to do the trip @ FL120 , unfortunantly, sans O2.
We did the trip in 2 hours and the headache ruined my day …
europaxs wrote:
According to the german rules you can fly up to FL 120 without O2 forever, between FL 120 and FL 130 for 30 minutes and above FL 130 you always have to use O2. So I suppose there’s no general problem for most of us. However, since I use O2 above FL 100, I feel much fitter and saturation is >90%.
It will be a problem for you, too, when part-NCO comes into force which it will on 25 August 2016 at the latest.
NCO.OP.190 Use of supplemental oxygen
The pilot-in-command shall ensure that he/she and flight crew members engaged in performing duties essential to the safe operation of an aircraft in flight use supplemental oxygen continuously whenever the cabin altitude exceeds 10 000 ft for a period of more than 30 minutes and whenever the cabin altitude exceeds 13 000 ft
Flyer59 wrote:
I have heard that some people suffer from headaches over FL100, but I have never seen it. I must admit though that when I started flying wit O2 over FL100 I did feel fresher and less tired even after long flights!
Until 2014 I have been flown up to FL 140 for hours without breathing oxygen, this was no problem at all. But my wife got headaches.
The reasons for saving oxygen where a high price for a refill, my maintenance company even doubled the price for the refill in 2013! And we did never found a company at our destinations for a refill after using oxygen. Now I do the refill myself using medical oxygen, doing this is simple but getting the necessary equipment wasn`t. Also we use a pulsoxymeter now, which show my PO2 at < 90 percent when passing FL 130, instantly climbing to 95 percent with oxygen. And yes, I feel fresher and less tired using oxygen. On our flights we carry an extra bottle, 2 Liters with cannula as an emergency equipment. For those who need O2 only occasionally this might be a cheap way to get oxygen since you get
2 Liters x 200 bar=400 Liters ! Setting the regulator to 2-3L/min gives you plenty of oxygen for crossing the alps.
highflyer wrote:
Now I do the refill myself using medical oxygen, doing this is simple but getting the necessary equipment wasn`t.
You just need trasfilling hose, pressure gauge and few fittings.
FL100 is ok for me, my oxygen saturation varies between 88-93. Even after a full day of flying I feel ok in the evening, albeit tired and a bit dehydrated. But for other pilot friends they are feeling totally hung-over, so very individual.
Never tried oxygen though so it’s difficult for me to compare.
A bit off topic, but I felt an incredible difference between a 12 hour flight on an A340 compared to the A380, but that’s perhaps more depending on the humidity than cabin pressure?
I used to get headaches and be fatigued after a flight at 10,000 to 12,000. I started using O2 and it made a great improvement, no more headaches. I returned from Oshkosh yesterday at 11,000 and before I put on the O2, I checked my saturation level using my oximeter, it was 88%. After a few minutes on O2, it was back to 98%.
In 2005 I was in a test group up to FL120. The results were eye opening to say the least. IIRC, some heart rates were approaching 120.
One problem in GA is that a lot of people eat chips and burgers and do no exercise. The one who could not read the altimeter was one of those.
I’m told by a couple of different aero medics that the correlation between fitness and hypoxia sensitivity is poor. I’m not advising eating lots of chips and doing no exercise, but I understand that being very fit does not necessarily mean immunity from hypoxia.
Eating a lot of chips may actually help, or so I’ve been told. So there may be an inverse correlation between fitness and oxygen saturation although I do not recall the exact mechanism other than it may have to do with faster bloodstream due to clogged arteries 
