A question that we frequently get asked is: Why is dry ice called dry ice?
At normal temperature and pressure, carbon dioxide (CO2) is a gas. When cooled, CO2 solidifies at -78 degrees C and is known as solid CO2 or dry ice.
Most compounds can exist in three states: as a solid, liquid and gas. Take water as an example. In its cold state, it is ice (solid). When it is warmed, it turns into water (liquid), and then when it is warmed further, it turns into steam (gas).
CO2 is different, as at temperatures warmer than -78 degrees C, it turns directly from a solid into a gas. This process is called sublimation, and because the solid never becomes a liquid, it is known as dry ice.
What Is Dry Ice Used For?
In its solid form, dry ice is often used as a refrigerant or coolant when transporting and storing other temperature-critical products. Solid CO2 is manufactured in the shape of pellets, slices or blocks and may be supplied loose in plastic bags or in insulated containers.
One issue with solid CO2, however, is that a small amount of dry ice, when it warms up, will produce a large volume of gas, approximately in a ratio of 1:800.
The Hazards Posed by Dry Ice
Cold Burns and Frostbite
At a temperature of -78 degrees C, dry ice is extremely cold. Contact with or close proximity to dry ice can cause cold burns. Prolonged exposure may lead to frostbite, hypothermia and other cold-related injuries.
Intoxication and Workplace Exposure Limits
CO2 is an intoxicant and is a hazard at low concentrations. For this reason, it has been assigned workplace exposure limits. For more information, refer to EH40 from the Health and Safety Executive.
Asphyxiation
Carbon dioxide gas is an asphyxiant, so great care must be taken by anyone who is handling, storing or using dry ice. Inhalation of either the cold gas or the local cold atmosphere can damage the lungs and may aggravate existing health conditions. The gas is heavier than air so any vapour will find its way to the lowest point in a work area and displace the oxygen.
Pressure Build-Up
If dry ice is placed in an unvented container such as a thermos flask, pressure will build up, potentially resulting in rupture of the container.
Safe Working with Dry Ice
Before working with dry ice, a full and sufficient risk assessment must be undertaken. Hazards must be identified, and suitable control measures must be put in place before the product is delivered to the site.
Safe systems of work must be developed and implemented for all operations where dry ice will be used. Operators must be trained in the hazards posed by dry ice and the safe systems of work that need to be employed when using the product. They must also be issued with and use appropriate personal protective equipment.
Dry Ice Training
If your staff require training in the safe handling and use of dry ice, please contact us on 01270 758890 or at admin@gassafeconsultants.co.uk.
We also have an online dry ice training workshop available if this method of training is more suited to your needs. Please contact us to discuss.
