Liquified gases evaporate to fill relatively large volumes, usually more than 700 times the volume of the liquid. These gases can displace oxygen, which can create a life-threatening environment in a small laboratory. Liquid helium and hydrogen are cold enough to solidify atmospheric air. Leaks in the storage systems for these gases may become plugged with solidified air. Particularly affected are pressure relief devices which, if plugged, may cause container over-pressure and failure.
Dry ice is solidified carbon dioxide.
Since the blood concentration of carbon dioxide controls human respiration, increases in the atmospheric concentration of carbon dioxide will stimulate more rapid breathing. Additionally, exposure to elevated carbon dioxide concentrations can cause headache, sweating, increased heartbeat, shortness of breath, dizziness, mental depression, visual disturbances, or shaking. Higher concentrations of carbon dioxide can easily cause a life-threatening atmosphere. Certain liquified gases, such as helium, hydrogen and nitrogen, have the ability to condense oxygen out of the air. Liquid cryogens, enriched with oxygen can cause fires or explosions when they come in contact with oxizidable materials.