Its advantages include lower temperature than that of water ice and not leaving any residue (other than incidental frost from moisture in the atmosphere).

While generally not very toxic, the outgassing from it can cause hypercapnia (abnormally elevated carbon dioxide levels in the blood) due to buildup in confined locations.

Dry ice is colorless, odorless, and non-flammable, and can lower the pH of a solution when dissolved in water, forming carbonic acid (H2CO3).

[1] At pressures below 5.13 atm and temperatures below −56.4 °C (216.8 K; −69.5 °F) (the triple point), CO2 changes from a solid to a gas with no intervening liquid form, through a process called sublimation.

Dry ice is non-polar, with a dipole moment of zero, so attractive intermolecular van der Waals forces operate.

[6] It is generally accepted that dry ice was first observed in 1835 by French inventor Adrien-Jean-Pierre Thilorier (1790–1844), who published the first account of the substance.

Such gases can be a byproduct of another process, such as producing ammonia from nitrogen and natural gas, oil refinery activities or large-scale fermentation.

Finally, the snow-like solid carbon dioxide is compressed into small pellets or larger blocks of dry ice.

[13][14] Dry ice is typically produced in three standard forms: large blocks, small (1⁄2 or 5⁄8 in [13 or 16 mm] diameter) cylindrical pellets and tiny (1⁄8 inch [3.2 mm] diameter) cylindrical, high surface to volume pellets that float on oil or water and do not stick to skin because of their high radii of curvature.

A standard block weighing approximately 30 kg (66 lb)[citation needed] covered in a taped paper wrapping is most common.

It is frequently used to package items that must remain cold or frozen, such as ice cream or biological samples, in the absence of availability or practicality of mechanical cooling.

This is done by dropping pellets into rodent tunnels in the ground and then sealing off the entrance, thus suffocating the animals as the dry ice sublimates.

Dry ice can be used for loosening asphalt floor tiles or car sound deadening material, making them easy to prise off,[30] as well as freezing water in valveless pipes to enable repair.

Similar procedures may be used in fabricating mechanical assemblies with a high resultant strength, replacing the need for pins, keys or welds.

[34] Dry ice has found its application in construction for freezing soil, serving as an effective alternative to liquid nitrogen.

[38] Dry ice and acetone forms a cold bath of −78 °C (−108 °F; 195 K), which can be used for instance to prevent thermal runaway in a Swern oxidation.

[45] Observations from the Uranus flyby by Voyager 2 indicates that dry ice is present on the surface of its large moons Ariel,[46] Umbriel[46] and Titania.

[48] Prolonged exposure to dry ice can cause severe skin damage through frostbite, and the fog produced may also hinder attempts to withdraw from contact in a safe manner.

Because it sublimes into large quantities of carbon dioxide gas, which could pose a danger of hypercapnia, dry ice should only be exposed to open air in a well-ventilated environment.

[30] For this reason, in the context of laboratory safety dry ice is assigned label precaution P403: "Store in a well ventilated place."

International Air Transport Association (IATA) regulations require specific diamond-shaped black-and white labelling to be placed on the package.

[54] In 2020, three people were killed at a party in Moscow after 25 kg of dry ice was dumped in a pool; carbon dioxide is heavier than air, and so can linger near the ground, just above water level.

One bar patron who accidentally ingested pellets from a drink suffered severe burns to his esophagus, stomach, and duodenum, causing permanent problems with eating.

Products that contain dry ice and prevent it from being accidentally ingested eliminate these risks while producing the desired fog effect.