Just some info.
The new Boeing 787 has higher humidity levels than any other plane. Since the fuselage is composite, they don't have to worry about corrosion induced by moisture.
Also, since it's composite they can pressurize the cabin to higher levels. So the air isn't as thin, and your ears don't pop. You feel less fatigued.
Contrary to what he says, air doesn't circulate around in a cabin, nor is it filtered. On most planes, cabin air comes out of the compressor section of the engine, very high pressure and temperature, probably around 400 F. This is known as Bleed Air. It goes through something called a Air Cycle Machine to cool it and then pumped into the cabin. There are outflow valves that continually dump air outside to maintain proper cabin pressure.
You are breathing the air that was -30F at 40,000 feet and got sucked into the engine and going to the ACM at 400F. That is why it is clean.