Common desiccants can be categorized by their ingredients as follows:
Silica gel desiccants: The shelf life is typically 1-2 years, with some products extending up to approximately 2 years. When the silica gel changes color to dark blue, dark pink, or dark green, it indicates moisture saturation and requires replacement or regeneration.
Activated carbon desiccants: The shelf life is generally 1-3 years (varies between sources; some sources indicate 1-2 years, others 2-3 years). Replacement is required when the color changes to dark gray.
Calcium chloride desiccant: It has strong moisture absorption but a shorter shelf life, typically 6 months to 1 year, and expires when it turns dark brown.
Food-grade desiccants: These are primarily made of food-grade silica gel or activated carbon. They have a shelf life of approximately 1 year and should be replaced if they become hard or have noticeable color changes.
Key Factors Affecting Desiccant Shelf Life:
The Impact of Storage Environment:
Temperature and Humidity Control: Desiccant should be stored in a dry, ventilated, and low-temperature environment. Avoid high temperatures and humidity, which can accelerate moisture saturation. For example, high temperatures can cause the desiccant to expire prematurely.
Pollution prevention: Avoid contact with harmful gases and chemicals. Activated carbon desiccants, in particular, are prone to absorbing odors and chemicals and should be stored separately and sealed.