In refineries and petrochemical plants the equipment needs to be checked during planned shutdown. This can require several weeks of downtime, if columns, vessels, heatexchangers and tanks have to be drained to remove deposits and armful gases such as hydrogen sulfide, benzene and other volatile hydrocarbons. Formation of iron sulfide is very common in oil refineries and ethylene plants. It easily accumulates in pipes, trays, structured packings, heat exchangers or vessels. Iron sulfide deposits must be removed or kept wet before inspection of the equipment. Otherwise there is a high potential for spontaneous ignition in the presence of oxygen due to the pyrophoric iron nature. Persons in charge try to minimize exposure of workers to any situation where pyrophorically induced fires or health risks could be initiated. This paper describes chemical cleaning technologies which provide significant reduction in the downtime of the distillation equipment with elimination of a potential risk of pyrophorically induced fires and harmful gases. It also gives an overview of advanced analytical and monitoring techniques.