I was attempting to avoid this portion of the conversation because it brings back nightmares of dealing with a professor that I considered to be one step above a member of the SS.
We are dealing with the Venturi effect when we are discussing outflow from a cone. Gas flow accelerates as it exits a cone due to the conservation of mass, but the pressure drops across the orifice. I do not see how a significant amount of O
2 can move into the flask when the pressure inside the flask is higher than it is outside of the flask. According to Graham's law, CO
2 and O
2 move from an area of higher pressure to an area of lower pressure.