Carbon dioxide is 1.5 times heavier than air. Fire extinguishers use to CO2 to eliminate the oxygen needed by fire. When carbon dioxide freezes, a snowlike solid called dry ice is produced. Because dry ice does not support combustion, is heavier than air, is easily generated and is cheap, it is a valuable fire extinguisher. You could reproduce a reaction like this, too.
Proper ventilation is required.
If you are using glass bottles or jars, the containers should be wrapped with a cloth.