Environmental control material holders can retain environmental control material within wafer carriers, allowing the environmental control material to protect wafers from moisture while also securing the environmental control material. The environmental control material holders may include a baseplate and tabs defining spaces to hold environmental control material, and can be configured to engage a handle of a wafer cassette. The environmental control material holders may retain one or more environmental control materials. Additionally, the environmental control material holders can be configured to also retain a humidity indicator.