Carbon dioxide is a gas at 1 atm of pressure and 25 °C. When this gas is taken to a pressure equal or greater than its vapor pressure it liquefies, to form liquid CO₂.
At 25 °C, the vapor pressure of CO₂ is around 60 atm, meaning that at this temperature the CO₂ is a gas, hence if we released liquid CO₂ from a container at 60 atm to aroom at 25 °C and 1 atm, it will pass from liquid state to a gas state. The CO₂ can not exist in a liquid form at 1 atm of pressure.
