By Grainger Editorial Staff 12/13/20
Dry ice is frozen carbon dioxide (CO2). In the dry ice manufacturing process, pure CO2 gas is first pressurized and cooled in order to turn it into a liquid. The liquefied CO2 is then fed into a dry ice production machine, where the pressure is released, a process which creates CO2 "snow" that is then compressed into pellets or blocks of dry ice.
The surface temperature of dry ice is –109.3° F (–57° C). Above this temperature, dry ice sublimes, or sublimates. Both words describe the same thing—when a substance turns directly into a gas without first becoming liquid. This means that dry ice will evaporate without leaving moisture or wetness.
Because dry ice is very cold but disappears without getting things wet or leaving liquid behind, it has many industrial applications. It's used to preserve foods, chemicals and medical samples and supplies, especially during transportation. It's also used for dry ice blasting, a cleaning process used on machinery and tools and for removing mold and graffiti.
Following these three tips can help minimize hazards when you're handling dry ice.
Dry ice can be stored in non-air-tight chests or buckets made from insulating foam to help slow the rate of sublimation. Dry ice will sublimate at any temperature above –109.3° F. The rate at which it sublimates can vary considerably depending on the quantity and form of the dry ice. A small amount of pellets will sublimate much more rapidly than a single large block, according to a report published by the Federal Aviation Administration (FAA).
Dry ice containers should be kept only in places with good ventilation.
Allowing dry ice to sublimate at room temperature is an effective way to dispose of it, but it's important to take precautions to help prevent hazards.
Q: Can dry ice cause carbon dioxide poisoning?
A: Dry ice can produce large quantities of carbon dioxide as it turns from a solid to a gas. Carbon dioxide is in the air we breathe, but it makes up only a tiny percentage of it (less than a tenth of one percent), and at high concentrations it has toxic effects. Carbon dioxide poisoning can be caused by dry ice in enclosed, poorly ventilated spaces.
Q: What are the symptoms of carbon dioxide poisoning?
A: Rapid breathing is an early symptom of carbon dioxide exposure. Other symptoms of carbon dioxide poisoning are similar to those of oxygen deprivation and include headache, dizziness and drowsiness.
Q: Is dry ice a cryogen?
A: Cryogens, also called cryogenic substances, are used to achieve extremely cold temperatures. Dry ice has a surface temperature of –109.3° F, which is very cold compared to the freezing temperature of water. However, dry ice is not a cryogen. Cryogenic temperatures are generally defined as being below –150° C, or –238° F, which is much colder than dry ice. Cryogenic substances include liquid oxygen (–297° F) and liquid nitrogen (–320° F). Learn more about cryogenic safety.
Q: Can I save dry ice in my freezer?
A: No. Dry ice turns to a gas at –109.3° F, so even a freezer will be far too warm to prevent that from happening. And dry ice should never be kept in a walk-in freezer, because it produces carbon dioxide that can be hazardous in poorly ventilated areas. A good way to preserve dry ice is in a non-air-tight insulated container such as a chest or cooler, the thicker its insulation the better, stored in a well-ventilated location.
The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.