Octavia: "Vinyl? Why are all the tanks empty?"
Vinyl: "Uh... definitely not because I tried refilling the smoke machines with them?"
Octavia: "...you are so incriminatingly specific sometimes, you know."

So, here's a fun thing that happens with pressurized tanks sometimes, they do occasionally run out of pressure! Whether that's through leaking, responsible usage, or irresponsible usage, eventually and inevitably they do have to be refilled.

Ideally though, this lack of contents and refilling happens before one desires to try and make use of them...