Q&A regarding Avatar

[ZenitYerkes]

I've got two:

Q: Why are the Na'vi blue?
A: Because of the high concentration of CO2 and other components in the atmosphere, hemoglobin, the responsible for oxygen transportation, turns darker; making the skin look blue. A similar effect can be experienced when cutting off blood circulation from a part of the body: cells begin to produce CO2 turning the skin of the affected area red, violet, purple and, finally, blue.

Q: Why can humans still breathe when there are bullet holes on their vehicles' windshields?
A: Pandoran air is denser than the air produced by these machines to allow their crew breathe. When a bullet hole is made, Pandoran air deposits in the lower stages of the vehicle, and slowly fills the cabin; however terrestrial air remains on the highest parts of it, making breathing still possible.

I hope this makes some kind of sense.