Dry Ice: What You Need To Know

1) What is dry ice?dry ice
Dry ice is solid Carbon Dioxide (CO2) with a low temperature of -78° C (-109° F). At atmospheric pressure, solid CO2 sublimates or changes directly to CO2 gas without a liquid phase.

2) How long are samples kept in dry ice? And does the long-term storage affect any sample analysis?
Samples can be kept frozen in dry ice for days, depending on the analytes/biomarker frozen stability. As dry ice has a limited shelf-life, long term storage of specimens can be jeopardized in case of insufficient replenishment of dry ice. For long term storage of specimens we recommend using a standard medical/scientific freezer instead of dry ice, with appropriate freezer’s temperature monitoring.

3) What are the factors that may increase the dry ice evaporation rate?
Dry ice sublimates at a rate of 3% to 8% per day, depending on:

-The thermal properties of the container
-The external temperature profile
-The size and shape of dry ice (big slabs of dry ice last longer than pelletized or snow dry ice, which sublimates faster)

For biological specimen storage/shipping purposes, it is recommended that dry ice come in nugget shape, which has an average sublimation rate and average shelf life.

4) Are there other risks to note, when handling samples in this condition?
Dry ice is the solid form of Carbon Dioxide (CO2) a natural byproduct of respiration, fermentation, and other industrial processes, existing as a colorless, odorless, and non-flammable gas. It is important to handle or store CO2, whether solid or gas, in well-ventilated areas to reduce the risk of asphyxiation for personnel. Dry ice, when offered for specimens transported by air, must be in packaging designed and constructed to permit the release of carbon dioxide gas and to prevent a build-up of pressure that could rupture the packaging.

5) Common mistakes made when using dry ice.
All of the below could lead to the cancelling of testing which could delay study timelines  and/or result in the patient resubmitting a sample.

a) When sites do not use a sufficient amount of dry ice to ensure stability during transit. This leaves the samples susceptible to thawing which could potentially compromise stability.

b) When sites use big chunks of dry ice (instead of the recommended nugget size) which can potentially damage the container or break it which contaminates the sample. The sample will be cancelled as ‘broken in transit.’

c) When sites do not use a collection bag and send their samples loose in dry ice. This could lead to loss of sample especially with smaller containers.

d) When sites fail to place dry ice in the foam. Samples are not maintained in frozen stability and therefore are potentially compromised.

Please be aware that investigator sites are responsible for properly training staff in the use of dry ice/dangerous goods according to your national regulations.  Covance does not provide or endorse one particular training program over another.  Click here for a list of some training providers.

This article originally appeared in 2015.