PCM stands for Phase Change Material.

PCM packs are packaged cold chain refrigerants similar to gel packs and cold packs designed to keep specimens in specific temperature ranges.

PCM packs are available for varying solid-to-liquid phase change temperatures, while a gel pack has a fixed solid-to-liquid change temperature of 0°C (32°F).

A phase change material absorbs cold energy as it changes its state from liquid to solid. During this process, it releases stored heat providing a warming effect. 

A phase change material absorbs heat as it changes its state from solid to liquid. During this process, it releases stored cold energy providing a cooling effect. 

The phase change temperature of a PCM during its melting and solidification is generally the same. This provides PCM the unique capability to maintain a constant temperature during phase change. 

PCM materials have a known thermal energy value stored or released during phase change. This helps determine the quantity and type of PCM needed for each unique application.

An organic PCM is a phase change material manufactured using hydrocarbon or fatty acid-based oils. In simple terms, organic PCMs are oils.

A phase change material manufactured using a water-salt-based mixture is largely termed an inorganic PCMs. Simply, inorganic PCMs are hydrated salts or eutectic solutions.

Dry ice is available in solid form, which is carbon dioxide gas that is solidified at a temperature of -78.5°C (-109°F). This temperature is far too cold for humans to safely touch. It can cause frostbite if held without protection. 

Dry ice sublimates into carbon dioxide gas. Improper ventilation can lead to the inhalation of large concentrations of CO2. This has harmful physical effects, including death. 

Most frozen products require a temperature range of -20°C to -5°C (-4°F to 23°F) during transportation and storage. 

A PCM with a phase change point of -25°C can safely meet this requirement without developing the risk of frostbite or gas inhalation.