Carbon dioxide is a food additive used as a propellant and acidity regulator in the food industry. It is approved for usage in the EU[19] (listed as E number E290), USA[20] and Australia and New Zealand[21] (listed by its INS number 290).
A candy called Pop Rocks is pressurized with carbon dioxide gas at about 4 x 106 Pa (40 bar, 580 psi). When placed in the mouth, it dissolves (just like other hard candy) and releases the gas bubbles with an audible pop.
Leavening agents cause dough to rise by producing carbon dioxide. Baker's yeast produces carbon dioxide by fermentation of sugars within the dough, while chemical leaveners such as baking powder and baking soda release carbon dioxide when heated or if exposed to acids.