In the episode "Lockdown", the blast doors descended, sealing off the living quarters and computer room from the rest of the Swan. After a short period of time, the doors retracted back into the ceiling automatically. This event has become known as the lockdown incident.
Chronology of the lockdown incident
John Locke, halted by the descended blast door during the lockdown incident
A garbled recorded message by a female speaker, ending in a countdown to zero, was broadcast throughout the Swan's speaker system. The female voice (played by Lynnanne Zager) said: "23 minutes to lockdown"; "17 minutes to lockdown"; "Please proceed...protocol...please proceed..."; "9...8...7...6...5...4...3...2...1".
The blast doors descended sequentially, sealing the living area of the station. The doors sealed off access to the bedroom, the two entrances to the computer room, the doorway from the living area to the main corridor and, oddly, the "window" in the dining nook.
The station's power was then disrupted as the lights flickered. Later, a different set of ultraviolet 'black' lights that ran vertically along the corners of the living area activated, revealing a previously hidden map of the Island on one of the doors. A short time later, the blast doors retracted into the ceiling.
It should be noted that the countdown timer in the computer room also reached zero during the time of the lockdown, but it not clear if the Swan's computer had any effect or control over the lockdown incident. The recording was first heard 23 minutes prior to the lockdown, the timer at this point had just over 47 minutes remaining; therefore, when the blast doors came down, they remained down for approximately 24 minutes.
At approximately the same time as the lockdown, a large pallet of DHARMA-branded provisions landed by parachute, with a flashing beacon, close to the entrance to the Swan. This supply drop appeared to be a restocking procedure and may have been connected to the lockdown. A note on the blast door map read: "ACTIVITY MINIMAL DURING LOCKDOWN AND RESTOCKING PROCEDURES".
Other lockdown incidents
Desmond triggers a Lockdown for his first time by briefly shorting two power supply wires in his flashback. ("Live Together, Die Alone, Part 1")
- Kelvin mentioned that Radzinsky figured out how to force a lockdown, implying it had been done on previous occasions. ("Live Together, Die Alone, Part 1")
- Kelvin and Desmond regularly forced a lockdown to work on the blast door map. ("Live Together, Die Alone, Part 1")
- Desmond forced a lockdown to keep Eko out of the computer room so that he and Locke could intentionally let the countdown timer run down to zero. ("Live Together, Die Alone, Part 1")
- In the non-canon Lost: Via Domus, Elliott Maslow was in the Swan when a lockdown incident trapped him inside, forcing him to push the button. During the lockdown, Elliott discovered the blast door map. ("Forty-Two")