[Retr0id]

there is generally plenty of ambient air in the earth's atmosphere

[dotancohen]

And how can that ambient air be stuffed into bags to control buoyancy?

[Retr0id]

https://en.wikipedia.org/wiki/Air_pump

[dotancohen]

An air pump will not compress the air such that it becomes dense enough to overcome the buoyancy of the helium. The idea is ridiculous.

[Retr0id]

Tell that to the airships I guess