Is Furadan used as a fumigant?

No, Furadan is not used as a fumigant.

Specifically, a fumigant designates a gaseous pesticide which poisons or suffocates pests within a covered, sealed environment. Furadan is a trade name for the toxic carbamate pesticide carbofuran whose original application was by granules or liquid. It serves as a contact and systemic insecticide against insect pests and nematicide against parasitic nematodes. It will be found particularly in use in the large-scale cultivation of corn, potatoes and soybeans.