What's it feel like on top of the world with no O2?

Lucky for me there is an altitude chamber just down the road in Colorado Springs. I took a day course there today that covers various flight issues related to awareness, fatigue, night vision and altitude! We spent about 90 minutes in a chamber and took a flight to 25,000ft where we then took off the 100% O2 to see what the effects of hypoxia are. I was kind of tingly but didn't have any serious affects before getting the O2 back on, I am sure I wouldn't of lasted too long!

The biggest thing I learned? How to deal with the mask. We were spending 30 minutes breathing 100% O2 to prepare for the flight and I got an itch on the end of my nose. I couldn't scratch it so it just got worse and worse and worse. All mind games, last I heard an itch can't kill you.