Furnace oil, fuel consisting mainly of residues from crude-oil distillation. It is used primarily for steam boilers in power plants, aboard ships, and in industrial plants. Commercial fuel oils usually are blended with other petroleum fractions to produce the desired viscosity and flash point.

Industrial heating: Furnaces are used in many industries to heat materials to high temperatures. For example, in the steel industry, furnaces are used to melt and refine metals.

Ceramics and glass production: Furnaces are used in the production of ceramics and glass. They are used to heat raw materials to high temperatures, which causes them to melt and fuse together.

Laboratory use: Furnaces are commonly used in laboratories for a variety of purposes, such as heating samples to high temperatures for analysis or sterilizing equipment.