Dry ice is solid CO2 with a low temperature of -78° C (-109° F). At atmospheric pressure, solid CO2 sublimates directly to vapor without a liquid phase. This unique property means that the dry ice simply “disappears” when it heats up, leaving no residue or waste to be cleaned.

The CO2 used to make dry ice is a natural by-product of several industrial manufacturing processes such as fermentation and petrochemical refining. The CO2 given off by the above production processes is captured and stored without losses until needed. When dry ice is used no new CO2 is produced. Instead, only the original CO2 by-product is released which is why using dry ice is considered to be “carbon-neutral” and environmentally responsible. Carbon dioxide (Chemical Symbol = CO2) is a natural byproduct of respiration, fermentation, and other industrial processes, existing as a colorless, odorless, and non-flammable gas. Its density at 25°C is 1.98 kg/m3 (0.123 lbs/ft3at 32°F), about 1.65 times that of air, which means that CO2 gas displaces oxygen in the environment (CO2 sinks below oxygen).
Dry ice is the solid form of CO2 and is white opaque in appearance. It is important to handle or store CO2, whether solid or gas, in well-ventilated areas to reduce the danger of asphyxiation.
The detailed table below shows the chemical and physical properties of CO2.

Dry ice sublimates or changes directly from solid to gas, without a liquid phase. The rate of sublimation must be taken into account when packing a container system since it gets smaller in size. Dry ice sublimates at a rate of 3% to 8% per day, depending on the thermal properties of the container and external temperature profile. One pound of dry ice will sublimate into 8.3 cu. ft. of carbon dioxide gas.

Slabs of dry ice last longer than pelletized dry ice, which sublimates faster.