This paper describes the methods and presents the results of the “Troitsk Nu-mass” experiment spectrometer cleanup after the in\ner volume (40 m3) and surfaces (160 m2) were contaminated by 5.2 GBq of tritium. The Troitsk Nu-mass experiment of the Institute for Nuclear Research of the Russian Academy of Sciences (Moscow) is designed to measure the spectrum of electrons from tritium decays in order to search for hypothetical particles—sterile neutrinos. Due to some equipment failures, the spectrometer internal volume was contaminated with tritium. The contamination made measurements impossible, and the research program stopped. Different methods were used for cleanup: vacuum extraction, hydrogen soaks, and water vapor soaks. As a result of detritiation, the background level of the main detector of the Troitsk Nu-mass spectrometer was reduced approximately by more than ten times, which made it possible to resume work. The results are consistent with the literature data obtained earlier for normal conditions in the air and can be used for detritiation of similar installations.