In an air pistol why is co2 the only gas i can use?

Question

And also, why does it smell like s***z when I puncture a hole thorough the cylinder.

Answer 1

Carbon dioxide has the highest static vapor pressure for any given temperature because it resists liquification and that makes it have a higher energy decompression rate [i.e. it expands more rapidly because there is no risk of recondensation upon rapid cooling within the working temperatures found within the air pistol.

Nitrous Oxide is used in whipping cream because it adds acidity and it has the ability to microscopically yet partially coagulate the cream which makes it slightly stiffer [like how bread stiffens from a saggy dough into a firm loaf upon heating] and therefore holding its shape as a foam longer. Atop this, because it can be a liquid upon refrigerating, it evaporates slower and therefore makes more of a foam and less of a jet plume, and keeps the cream "inflated" longer.

Nitrous Oxide would cause condensation and corrosion of an air pistol as well as increase the possibility of the gun oil igniting as nitrates formed from it.

Answer 2

of all gases CO2 is the least dangerous when compressed. it may also have something to do with CO2 not having a liquid phase at normal temps and pressures.