Sector 3 Restore the Cooling Installation Timer Mission first plays in the Navigation Room of Sector 5, where Samus Aran is given instructions by Adam to fix the Main Boiler's cooling unit. As implied by its title, this music plays alongside a six minute countdown timer as Samus rushes to Sector 3. In the Main Boiler Control room, it also serves as the boss theme against the scientist who reveals himself to be a Core-X.
Sector 3 Restore the Cooling Installation Timer Mission plays another time during the mission in Sector 5 where Adam instructs Samus to find and terminate Nightmare, and stops as soon as she enters Nightmare's room.
Sector 3 Restore the Cooling Installation Timer Mission is played again after the Restricted Laboratory is detached and Adam sends Samus to report to a Navigation Room. Once Samus uses an Elevator to Sector 1, it will play throughout the entire BSL Station (barring a few exceptions, such as Neo Ridley's room) until Samus enters a Navigation Room and speaks with Adam once again.
Sector 3 Restore the Cooling Installation Timer Mission is played one last time during the final boss battle against the Omega Metroid. Here, the theme starts playing once Samus absorbs the Core-X of the SA-X and gains the Ice Beam. Once again, this boss battle is under a time limit, with Samus needing to kill the Omega Metroid and escape the BSL Station before it impacts SR388.
Sector 3 Restore the Cooling Installation Timer Mission has a more orchestral instrumentation than standard Metroid fare, albeit with compressed MIDI samples. It prominently features brass and horns playing the melody, accompanied by high strings and militaristic percussion. This makes the song reminiscent of a march, similar to other Fusion tracks such as Facing a Huge Reaction and Last Instructions. Compared to those songs, however, this theme is less triumphant and more foreboding in order to fit the dangerous situations where it is played. It can be heard here: