[RouxStir]

"The same thing can happen by drinking water that is too pure. This is why it's dangerous to drink distilled water"



Same thing goes for air that is too pure. Don't breathe air when you are outside of the city...it'll kill you, it will.

[Soothesayer]

Not sure about air but pure oxygen can kill you.

[aruanan]

Same thing goes for air that is too pure. Don't breathe air when you are outside of the city...it'll kill you, it will.

Even the purest of air is still a mixture of gases. Even though it's about 78% nitrogen, breathing only nitrogen will kill you. Even though you need only about 20% oxygen, breathing pure oxygen for too long can be harmful.