What Is Dry Ice? Can You Eat It? Production and Applications

Dry ice is increasingly familiar in everyday life, with applications ranging from healthcare and agriculture to industry and entertainment. Yet many people still wonder what it is, whether it can be eaten, and what risks it poses. In this article, SIGVN explains its properties, production process, uses, and essential safety precautions.

1. What is dry ice?

In Vietnam, dry ice is also known by names meaning dry ice, smoke ice, fog ice, or CO₂ ice. Scientifically, it is the solid form of carbon dioxide (CO₂), a substance normally encountered as a gas.

Its defining property is sublimation: at atmospheric pressure, it changes directly from a solid into a gas without melting into a liquid. Its sublimation temperature is approximately −78.5°C (−109.3°F).

Unlike ordinary ice made from water, dry ice is extremely cold and consists of closely packed molecules in a crystalline solid. This helps explain its powerful cooling effect. It leaves no liquid water behind when it has completely sublimated, making it useful where moisture is undesirable.

Thanks to its cooling performance and relatively accessible cost, dry ice is widely used to preserve food, seeds, and biological tissues, as well as for industrial cleaning.

2. A brief history of dry ice

CO₂ occurs naturally in the atmosphere. It is a colorless gas, generally described as odorless and tasteless, with a density about 1.5 times that of air. Under suitable pressure and temperature conditions it can be converted into solid, opaque white carbon dioxide; at atmospheric pressure, this solid sublimates at approximately −78.5°C.

The development of dry ice followed the study of carbon dioxide’s physical properties in the early nineteenth century:

• 1834: French chemist Charles Thilorier first observed CO₂ snow when opening a vessel containing compressed liquid carbon dioxide. Rapid evaporation cooled part of the remaining material into a snow-like solid.
• The nineteenth century: Solid CO₂ remained primarily a laboratory material, with little commercial use.
• 1897: British inventor Herbert Samuel Elworthy patented the use of solid CO₂ for making soda water.
• The 1920s: Commercial production began in the United States. The term “Dry Ice” was registered by Prest Air Devices in 1925, alongside production for refrigerated rail transport and cargo preservation.
• From the mid-twentieth century onward: Dry ice became an important cold-chain material. It was particularly valuable before domestic electric refrigerators became widespread and remains widely used today.

3. How is dry ice produced?

The process begins with a supply of high-purity CO₂, often recovered as a by-product from refineries, ammonia synthesis, or other chemical processes. The gas is collected and purified to remove contaminants and meet the applicable safety requirements, including food-grade requirements when intended for food applications, before entering the solidification line.

1. Liquefaction: Carbon dioxide is compressed and cooled at high pressure into a liquid, then stored in specialized tanks.
2. Phase change: Liquid CO₂ flows through a pipe into an expansion chamber. The sudden drop from high pressure to atmospheric pressure causes rapid expansion and evaporation, producing CO₂ snow at around −78.5°C.
3. Compression and molding: A hydraulic press applies substantial force—around 60 tonnes in the process described—to compact the snow into large, dense blocks within minutes.
4. Cutting to size: An automated pneumatic saw cuts the blocks into standard commercial sizes or sizes suited to customer requirements.
5. Storage and transport: The finished product is placed in specialized insulated containers to limit heat gain and sublimation during storage and delivery.

4. Common applications of dry ice

Food and pharmaceuticals: Dry ice helps keep ice cream, fresh produce, and frozen foods cold during long journeys. The CO₂ released through sublimation can also inhibit the growth of certain bacteria and molds. Its low temperature is useful for preserving vaccines, blood, biological tissues, and living cells that require deep cooling.

Industrial cleaning: Dry ice blasting propels small pellets at high speed to remove grease, paint, and deposits from machinery. It can clean suitable surfaces without abrasive media and without leaving chemical cleaning-agent residues.

Arts and entertainment: When placed in warm water, dry ice produces a dense, low-lying fog effect that is widely used on stages and at events.

Preservation of human remains: Its intense cooling can help slow decomposition by rapidly cooling tissues.

Other applications: Dry ice is used for shrink-fitting metal components, slowing the opening of flower buds in agriculture, and various other technical processes.

5. Can dry ice be eaten? Important safety precautions

No. Never eat dry ice or put it in your mouth. Its extremely low temperature can cause severe cold burns, tissue damage, and injury to the lining of the mouth within seconds. Always use suitable insulated gloves or tongs when handling it; never touch it with bare skin.

Asphyxiation risk: As dry ice sublimates, it releases large quantities of CO₂. In enclosed or poorly ventilated areas, this gas can displace oxygen and create a dangerous atmosphere. Use and store dry ice only in well-ventilated areas.

Container rupture risk: Never store dry ice in an airtight bottle, jar, plastic box, or tightly sealed insulated container. The gas released during sublimation needs a safe escape route; otherwise, pressure can build up and cause the container to rupture.

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