A molecule consisting of one atom of carbon and two atoms of oxygen which is a major combustion product of the burning of organic materials. Carbon Dioxide (CO2) is the result of complete combustion of carbon. In the gaseous form, CO2 is used as a fire extinguisher. In the solid form, CO2 is known as dry ice. CO2 is heavier than air, with a vapour density if 1. 53 (air = 1. 00)