Fumed

Fumed is the past participle of the verb fume and is used in different ways across science, industry, and everyday language. As an adjective, it describes something that emits or is exposed to fumes, vapors, or smoke. In chemistry and manufacturing, fuming also refers to processes that generate vapors deliberately, such as fuming sulfuric acid or fuming nitric acid, where visible vapors are produced from concentrated reagents. The term can also describe a reaction or environment influenced by fumes.

A notable technical use is fumed silica, also called pyrogenic silica. It is an amorphous form of silicon dioxide produced by flame hydrolysis of silicon compounds in a high-temperature flame. The resulting ultrafine particles have a very large surface area and form loose, fluffy powders. Fumed silica serves as a rheology modifier and thickener in paints, coatings, adhesives, and cosmetics, and can act as a filler in elastomers. It exists in hydrophilic forms and in hydrophobic variants that have been surface-treated to repel water, affecting dispersibility in different formulations.

Safety considerations for fumed silica are primarily occupational. The material is largely inert, but inhalation of fine particles can pose respiratory risks, so appropriate ventilation and protective equipment are advised during handling.

Etymology traces to the word fume, from Latin fumus, with usage in English dating to early modern chemistry. In common speech, fumed may simply describe something that has emitted fumes or the act of producing fumes in a process.