# Chemical reaction to produce 5 liter of gas [closed]

I'm looking for a chemical reaction in order produce about 5 liter of harmless gas.

The goal is to start with something that takes as little volume as possible to start with, and reacts to fill up a bag, and also not producing too much heat to not harm the bag.

I'd go with carbon dioxide $\ce{CO2}$ as a rather convenient gas which is non-flammable and doesn't require special equipment or exothermic reaction to synthesize. Common ways of obtaining $\ce{CO2}$ gas are:
• Dry ice + ambient temperature above $\pu{−78.5 ^\circ C}$;
$\ce{O2}$ and $\ce{H2}$ are rather dangerous in terms of flammability, also common synthetic methods require exothermic reactions.
$\ce{N2}$ is inert, but not easy to come by; the most effective way of obtaining nitrogen would be thermal decomposition of azides $\ce{M^IN3}$ and ammonium nitrite $\ce{NH4NO2}$.