The Self-destruct control room is a room located on Level 28 of Stargate Command. It houses the Self-destruct mechanism which requires two officers (per the Two-man rule) to activate and has a five minute countdown. When accessed directly and not from the Stargate Operations room, it requires physical keys in addition to authorization codes.
When Replicators invaded the SGC in 2002, Major General George S. Hammond and Major Samantha Carter activated the device but deactivated after Reese shut down the Replicators. It was activated once more by Anubis in Brigadier General Jack O'Neill's body two years later in 2004 with the help of Major Kearney but Carter was able to deactivate it from the Stargate Operations room. (SG1: "Menace", "Lockdown")