What is the required method for sending specimens that must remain frozen?

The correct method for sending specimens that must remain frozen is on dry ice. Dry ice, which is the solid form of carbon dioxide, maintains a temperature of -78.5 degrees Celsius (-109.3 degrees Fahrenheit), making it the most effective option for keeping specimens at or below freezing temperatures during transit. This is particularly important for biological samples or other sensitive materials that can degrade or become nonviable if they thaw.

Using ice packs, while effective for cooling items, does not maintain temperatures as low as dry ice and can result in specimens partially thawing, which could compromise their integrity. Refrigeration is designed to keep items cold but may also allow temperatures to rise above freezing, which would not be suitable for specimens requiring constant freezing conditions. Sending items at room temperature is not appropriate for specimens that need to remain frozen, as this would likely lead to thawing and degradation.