On The Skeld, Reactor is a room located in the corridor across from Security. It contains two vents, with the upper one connecting to Upper Engine, and the lower one connecting to Lower Engine. While the room's reactor typically glows blue, it will begin to glow red if Sabotaged, with paths to the handprint scanners lighting up. A fake Divert Power panel is shown but cannot be used. When inside the room, background ambient sounds are heard.
On MIRA HQ, Reactor is connected to Laboratory, and contains a massive reactor with a claw that emits a laser, several computers, and two fingerprint scanners that are used to resolve Reactor Meltdown, similar to The Skeld. The room's reactor also glows red during Reactor Meltdown. To reach Reactor, Crewmates must first go through Decontamination. A vent is located on the left below, allowing Impostors to enter without going through Decontamination. Several one-way windows can also be seen through from the hallway side of Reactor.
Impostors can Sabotage Reactor, starting Reactor Meltdown. Players are given 30 to 45 seconds to resolve the Sabotage; 30 seconds on The Skeld and 45 seconds on MIRA HQ. To resolve, two players must scan their hands at different stations simultaneously. If it is not resolved in the allotted time, The Impostors will win.