Carbonation levels are difficult to control when making soda with yeast. The method described above allows yeast to produce carbon dioxide for three days at room temperature. When the soda is refrigerated, the yeast becomes dormant and CO2 production nearly stops. If the soda is not refrigerated after bottling, pressure will continue to build inside the bottles and the soda may erupt in a gusher when opened. Glass bottles may even explode. Just a word of warning. Soda is fun, easy and safe to make at home, but please be careful.