Mazut is a low-quality heavy fuel oil that is used in power plants and similar applications. It is a viscous, dark, and heavy fuel oil that is almost exclusively manufactured in Russia, Kazakhstan, Azerbaijan, and Turkmenistan. Mazut-100 is a fuel oil that is manufactured to GOST specifications, for example, GOST 10585-75 (not active) or GOST 10585-2013 (active as per December 2019) . Mazut is typically used for larger boilers in producing steam since the BTU content is high. In the United States and Western Europe, mazut is blended or broken down, with the end product being diesel. Mazut may also be used for heating houses in the former USSR and in countries of the Far East that do not have the facilities to blend or break it down into more conventional petrochemicals. In the West, furnaces that burn mazut are commonly called "waste oil" heaters or "waste oil" furnaces.