What is Dry Ice and How Is It Made?

Anyone who remembers “ice boxes” may recall the regular deliveries of massive blocks of ice that kept their meat and food cool inside the icebox, which was a precursor to the refrigerator. When those bricks melted and turned to liquid, however, they made a big mess.

With dry ice, you don’t have that difficulty. Because it’s exactly what it says on the tin: dry ice. And as it “melts,” it really transforms from a solid to a gas. Carbon dioxide gas that has been compressed to a high pressure is known as dry ice.

Carbon dioxide undergoes a solid-liquid-gas metamorphosis in response to pressure, similar to how the nature of water changes as the sea level rises, boiling at lower temperatures and pressures. CO2 is neither a liquid nor a gas at atmospheric pressure. It becomes a liquid when contained within the high-pressure chamber of a fire extinguisher.

To generate dry ice, liquid carbon dioxide is discharged from a high-pressure container, followed by fast evaporation of some of the gas into the air, resulting in near-instantaneous cooling of the remaining liquid to the freezing point. The ice/foam-like product is subsequently compressed, resulting in blocks of ice with a surface temperature of roughly -109F.

Dry ice is ideal for transporting perishables across long distances due to its high density and delayed evaporation following compression. Because any evaporation converts the dry ice to a gas that is discharged into the air, there are no messy puddles of water. As a result, dry ice should never be transported in a closed vehicle or stored in an enclosed space without enough ventilation. When CO2 levels in regular air reach to around 5%, they become poisonous.