Frozen solid carbon dioxide (CO2) at a temperature of -87.5 degrees centigrade which produces clouds of steam-loaded CO2 gas forming a low-lying mist or fog when dropped into boiling water. Although non-toxic, caution is required in the storage and handling of dry ice because of its extreme cold. Water is boiled in a large tank offstage, into which the dry ice is lowered in a basket. Fans and ducts then direct the gas onto the stage. Dry ice does not support life, so care should be taken that small animals, actors etc. are not below the level of the dry ice for more than a few seconds.