Carbon dioxide gas/vapor is colorless, odorless, and about 1.5 times as heavy as air, while dry ice is white/opaque. Carbon dioxide can exist simultaneously at its triple point as a solid, liquid, and gas at a temperature of –69.9 °F (–56.6 °C) and a pressure of 60.4 psig (416 kPa). At temperatures and pressures below the triple point, carbon dioxide can be either a solid (dry ice) or a gas, depending upon temperature conditions. At temperatures and pressures above the triple point and below 87.9 °F (31.1 °C), carbon dioxide liquid and gas can exist in equilibrium in a closed container.

Precautions for handling dry ice are found in CGA G-6.9, Dry Ice. General precautions for the safe handling of gaseous carbon dioxide are contained in CGA G-6, Carbon Dioxide.

Dry ice has a temperature of –109.3 °F (–78.5 °C) at 1 atmosphere and must be protected during storage with thermal insulation in order to minimize loss through sublimation. When entering low or confined areas where a high concentration of carbon dioxide gas may be present, use a self-contained breathing apparatus (SCBA) or supplied-air respirator. Do not use a cartridge-type respirator.

Dry ice should be stored in a cool, well-ventilated area in well-insulated storage containers designed to prevent pressure buildup. If transporting in the passenger compartment or trunk of a vehicle, limit dry ice to small quantities and open all windows or ensure constant supply of fresh air for the duration of the trip.

Care should be taken when handling dry ice. Use protective gloves such as work gloves or ice tongs; do not handle dry ice with bare hands. Blocks of dry ice can weigh in excess of 50 lb (22.7 kg) and can cause injury if dropped.

Dry ice is extremely cold and can freeze human tissue on contact. Never place dry ice in your mouth. If swallowed, the dry ice will rapidly expand and can cause serious injury or death.

The best method for disposal is to allow the dry ice to sublime or evaporate to the atmosphere in a well-ventilated area where no buildup of carbon dioxide vapor can occur. Such areas should be secured to ensure controlled access to authorized personnel only. Unused dry ice may be returned to the supplier for proper disposal.

Do not dispose of dry ice:

• in sewers, sinks or toilets;
• in bodies of water;
• in garbage receptacles;
• on the ground when located over underground utilities;
• in unprotected boxes; or
• in areas accessible to the general public.

Because dry ice rapidly sublimates, or converts, into carbon dioxide gas ventilate adjacent enclosed areas to prevent the formation of dangerous concentrations of carbon dioxide. A concentration of 3% of carbon dioxide can be dangerous while higher concentrations can be lethal. Persons including rescue workers should not enter areas in which the carbon dioxide content exceeds 3% unless wearing an SCBA or supplied-air respirators (see the Physiological Effects tab).

Inhalation. Persons who have inhaled large amounts of carbon dioxide and are exhibiting adverse effects such as rapid respiration and headaches should be removed to fresh air immediately, if safe to do so. Perform artificial respiration if breathing has stopped. Keep the victim warm and at rest and obtain medical attention at once. Fresh air and assisted breathing (if required) is appropriate for all cases of overexposure. Recovery is usually complete with no residual effects.

Skin contact. In case of frostbite from contact with dry ice or cold gases, place the frostbitten part in warm water, 100 °F to 105 °F (37.8 °C to 40.6 °C). If warm water is not available or is impractical to use, wrap the affected part gently in blankets. Do not rub. Consult a physician.

Eye contact. If the eyes are involved, obtain prompt medical attention. The only appropriate first aid measure is a soft sterile pad held in place over both eyes.

Carbon dioxide is normally present in the atmosphere at about 0.035% by volume. It is also a normal end-product of human and animal metabolism. The greatest physiological effect of carbon dioxide is to stimulate the respiratory center, thereby controlling the volume and rate of respiration. It is able to cause dilation and constriction of blood vessels and is a vital constituent of the acid-base mechanism that controls the pH of the blood.

Carbon dioxide acts as a stimulant and a depressant on the central nervous system. Increases in heart rate and blood pressure have been noted at a concentration of 7.6% in air, and dyspnea (labored breathing), headache, dizziness, and sweating occur if exposure at that level is prolonged. At concentrations of 10% and above, unconsciousness can result in 1 minute or less. Impairment in performance has been noted during prolonged exposure to concentrations of 3% carbon dioxide even when the oxygen concentration was 21%.

Gaseous carbon dioxide is an asphyxiant. Concentrations of 10% or more can produce unconsciousness or death. Lower concentrations can cause headache, sweating, rapid breathing, increased heartbeat, shortness of breath, dizziness, mental depression, visual disturbances, and shaking. The seriousness of the latter manifestations are dependent upon the concentration of carbon dioxide and the length of time the individual is exposed.

OSHA provides a list of occupational exposure limits (OELs) for carbon dioxide. Please refer to OSHA’s website https://www.osha.gov/annotated-pels/table-z-1 for more information.

Physical constants can be found in the CGA Handbook page for Carbon Dioxide