Carbon dioxide gas is colourless and odourless gas or extremely cold liquid under pressure or refrigeration. It will not burn. Carbon dioxide is a COMPRESSED GAS. It Can displace oxygen in air, it may accumulate in low areas and is a confined space hazard. Carbon dioxide is a very mild central nervous system depressant. Very high concentrations may cause headache, nausea, dizziness, sweating, restlessness and disorientation. Liquefied gas may cause frostbite.

CO₂ gas is used for the carbonation of beverages; for pH control; as a chemical intermediate; in chemical processing; as a food preservative; as an inert "blanket"; and in enhanced oil and gas recovery. Liquid CO₂ is used as a refrigerant; for low temperature testing of aviation, missile and electronic components; as a fire-extinguishing agent; for stimulation of oil and gas wells and for controlling temperature in chemical reactions. CO₂ gas is a by-product of carbonaceous fuel combustion; is found in naturally occurring gases; is a product of animal and human metabolism, and is found naturally in the atmosphere (about 0.035%).

Depending on temperature and pressure, carbon dioxide (CO2) can exist as a solid, liquid or a gas. This review is for CO2 gas which is shipped or stored in high pressure cylinders as a liquid under its own vapour pressure of 5729 kPa at 20 deg C, in insulated containers as a refrigerated liquid, or is made and used on-site. May contain nitrogen, oxygen, argon, hydrogen, carbon monoxide, hydrogen sulfide and amines as impurities, depending on source.

Carbon dioxide gas is also known as carbonic acid anhydride, carbonic acid gas, carbonic anhydride, carbon oxide, CO₂, liquefied carbon dioxide, refrigerated carbon dioxide, anhydride carbonique, and carbon dioxide liquid.

Its CAS Registry Number is 124-38-9. This number is assigned by the Chemical Abstracts Service (CAS) in the United States and is used as a unique identifier number world-wide.