What Are the Two Types of Cold Chains?

Cold chains are typically classified in two distinct ways: by temperature range (chilled vs. frozen) and by the equipment/packaging used to maintain it (active vs. passive). 

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1. By Temperature Range

Cold chains are divided based on the specific environment required to maintain the stability of perishable goods. 

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Chilled Chain: Maintains temperatures above freezing, typically between +2°C and +8°C. It is designed for fresh produce, dairy products, and pharmaceuticals such as standard vaccines. 

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Frozen/Cryogenic Chain: Keeps products at sub-zero temperatures, typically ranging from -20°C to -150°C or lower. It is used for frozen foods, meat, biological products, and highly sensitive mRNA therapies. 

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2. By Equipment and Technology

Cold chains can also be classified by the physical method used to generate and maintain cooling. 

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Active Cold Chain: Relies on powered mechanical refrigeration units (such as battery- or fuel-driven systems) to circulate cold air into the payload area. These are ideal for large-scale shipments, offering high protection against temperature fluctuations and the ability to actively adjust conditions. 

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Passive Cold Chain: Uses non-mechanical methods to maintain temperature. These rely on highly insulated thermal containers combined with refrigerants such as gel packs, wet ice, or dry ice. They are typically used for smaller shipments, such as meal kit subscriptions or direct-to-consumer medical deliveries.