Answer is: rapid chemical reaction where gas is released.
This gas is probably carbon carbon(IV) oxide.
Other exampe, chemical reaction:
NaHCO₃ + HCl → NaCl + CO₂ + HCl.
Reaction occurs between sodium bicarbonate (sodium hydrogen carbonate) and hydrochloric acid. For example, hydrogen carbonate mixed with water is used like antacid (neutralizes stomach acidity), contverts stomach acid (hydrochloric acid) to carbon dioxide.