Carbon dioxide is a chemical compound composed of two oxygen atoms and one carbon atom (CO2). At standard pressure and temperature it is in its gaseous state and exists in Earth's atmosphere as a trace gas. It is a vital component in biological processes such as photosynthesis. Carbon dioxide is a colourless, odourless gas and is nearly 1.5 times the density of air.
Carbon dioxide freezes at -109.3 degrees Fahrenheit and forms dry ice. It does not "melt" in the sense that water ice melts. Because of its much lower temperature compared to water ice, 1 kilogram of dry ice cools as well as 2 kilograms of water ice. Another advantage of dry ice over water ice is that there is no intervening liquid stage between its solid and gas form. Therefor, it leaves no watery mess or residue once it "melts."
The main function of a living organism's respiratory system is to exchange oxygen and carbon dioxide. Carbon dioxide enters the body through the air you breathe As blood is pumped through the pulmonary artery into the lungs, the blood releases its carbon dioxide contents into the lungs and is the primary gas that is exhaled when you breathe out. Around 0.3 litre of carbon dioxide is transferred out of the blood each minute.
The largest man-made producer of carbon dioxide gas is fossil fuel combustion, especially as produced in cars and industrial processes. However, natural processes such as the decay of vegetation emit far more carbon dioxide into the atmosphere. Carbon dioxide is also released from within the Earth through volcanic eruptions and huge bubbles that rise through the oceans.
If a living organism is locked in an airtight room, it will die of carbon dioxide poisoning before oxygen suffocation.
In 1986, a cloud of carbon dioxide was released by Lake Nyos in Cameroon that suffocated 8,000 animals and more than 1,700 people.
The polar caps of Mars are mostly made up of carbon dioxide.