Alarms

Alarms are a gameplay mechanic in GTFO. When an alarm is triggered, hordes of sleepers will spawn and converge on the players until the alarm is deactivated or the expedition is completed.

Alarms are often tied to a bioscan sequence, and will continue until all scans in that sequence have been completed. Alarms, and their associated bioscan sequences, will be often be tied to opening Security Doors, and must be completed in order gain access to the next Security Zone. However, they can also be triggered when completing a Reactor Shutdown or Activate Generator Cluster objective. Alarms tied to uplinks are instead tied to the uplink verification process, and will end once the uplink is complete.

Alarms often have a ramping property, with the number or frequency of enemies spawned in each wave will rise in severity the longer the alarm persists. For that reason, completing the bioscan sequence tied to the alarm is an immediate priority for players.

The rules for where enemies can spawn during an alarm is covered in the Enemy Spawning page.

Error Alarms[]

Error alarms are not tied to a bioscan sequence or uplink, and instead continue until a suitable event deactivates them, such as inputting a DEACTIVATE_ALARMS command on an appropriate terminal or by completing an objective. Often, an Error Alarm cannot be deactivated and will persist until the expedition is completed.

Error alarms are often initiated after the players complete one of the objectives in the expedition, step on the Extraction Scan (sometimes referred to as an Extraction Alarm), or by interacting with a Security Door.

Alarm Types[]

In addition to the more typical alarm types, some alarms will spawns waves in noticeably different ways:

Diminished Alarm[]

Diminished Alarms typically spawn more frequent waves with fewer enemies. With waves spawning more frequently, often waves will spawn from multiple directions. It is recommended players defend against the incoming hordes as evenly as possible.

Surge Alarm[]

A surge alarm continues to spawn enemies until the spawn cap is reached, which can cause a team to be quickly overwhelmed. Each enemy killed will immediately spawn a new one as part of the surge. Surge alarms are incredibly dangerous, even to well prepared teams, as they will contain substantially more enemies than any other type of alarm.

Bioscan Sequences[]

Bioscans are characterized by a holographic circle that indicates the scan position and radius. Between bioscans, a white line will indicate where the next scan will spawn. In the case of a split scan, where multiple scan locations will appear, the white line will first trace to a given point before splitting into the appropriate number of lines.

If two bioscans overlap, then players can progress both of them at once. Downed teammates do not count as being within a bioscan, and must be revived before they can contribute to the scan.

Class[]

Example of the text describing an alarm

Alarms tied to a bioscan sequence will have an associated class. Alarms are classed with roman numerals, where the roman number indicates the number of bioscans that must be completed in order to deactivate the alarm. Many bioscan sequences will begin with a team scan, and the class includes this scan, so a class IV (4) alarm would typically consist of the team scan followed by three other types of bioscans. Most alarms have a class range from II (2) to VIII (8). Higher classed alarms are found deeper in The Complex.

Scan Types[]

Aside from the class of the alarm, the game may also communicate which types of scans will be involved. When doing so, an M or MIXED alarm will contain a mix of different scan types.

Team Scan[]

Team scans require all members of the team to be present for the scan to progress. If a team member leaves the scan then the scan progress will pause until all members are back in the scan.

Some bioscan sequences feature enlarged team scans, these behave identically to a regular team scan, except that the area they cover is larger and that they generally take longer to complete.

Despite requiring the full team, some team scans still progress faster with more players inside. An example of such scaling is shown below:

Number of Players	Scan Duration (seconds)
1	10.64
2	7.69
3	6.99
4	6.66

Small Red Scan[]

Small red scans consist of a small red circle, and are most typically part of a split containing four such scans.

Small red scans will progress faster with more players inside, up to a maximum of two players.

Number of Players	Scan Duration (seconds)
1	3.33
2+	2.5

Big Red Scan[]

Big red scans consist of a large red circle. They are rarely part of a split containing two or three of them, but are most commonly the only scan that spawns for that step in the bioscan sequence.

Big red scans will progress faster with more players inside, up to a maximum of four players.

Number of Players	Scan Duration (seconds)
1	20
2	8.33
3	6.99
4	6.66

Due to how the scan scales with number of players, when the sequence involves a split of two big red scans (and they deploy at roughly the same time), the optimal arrangement of a four-player team is a two-two split.

Cluster Scan[]

A cluster scan consists of a small orange circle, and is always part of an eight-way split.

Cluster scans will progress faster with more players inside, up to a maximum of two players.

Number of Players	Scan Duration (seconds)
1	1.33
2+	1

The term cluster is also used by the game to indicate a scan sequence that includes other types of scans which will split (e.g. a "Class III S Cluster scan" could contain a scan sequence that includes a three-way split of S scans).

S Scan[]

An S scan consists of a violet hexagon. S scans function similar to a normal team scan, requiring all team members to stand within the scan zone, but when the scan is interrupted because a team member is missing, scan progress decreases over time.

There are three commonly used variants of S scans, small, large and huge. Several bioscan sequences consist solely of a single huge S scan.

Despite requiring the full team, S scans still progress faster with more players inside.

Huge S scans
Number of Players	Scan Duration (seconds)
1	143
2	125
3	111.11
4	100

Large S scans
Number of Players	Scan Duration (seconds)
1	100
2	50
3	33.33
4	25

Small S scans
Number of Players	Scan Duration (seconds)
1	11.76
2	11.11
3	10.53
4	10

Room Scan[]

A room scan is a unique scan variant that consists of a single enormous scan that envelopes the entire room. It shares the mechanics of an S Scan, with scan progress decreasing when not all players are in the room.

T Scan[]

A T scan is a unique scan variant with the notable catch that it moves during scan progress. This scan can have some properties from other scan types such as team scans. In the case of a team T scan, the scan will require the full team before moving, and will stop moving whenever the full team is not in the scan.

Extraction Scan[]

Extraction scans consist of a large red circle. They are never part of a regular bioscan sequence, and only appear at the end of levels and must be completed to finish the expedition.

The duration of an extraction scan is highly level dependent. However, some will progress faster with more players inside, with an example shown below:

Number of Players	Scan Duration (seconds)
1	20
2	16.66
3	14.3
4	13.33

Extraction scans that require an objective item inside them to progress will never progress faster with more players inside. These scans can safely be completed by one player.

Stealth Scan[]

A stealth scan consists of a small green circle. Stealth scans indicate bioscan sequences that are not tied to an alarm.

Trivia[]

Strikers and Shooters spawned by alarms have a different appearance than those found dormant throughout The Complex, having a darker coloration.
The alarm deactivation from entering the DEACTIVATE_ALARMS (or similar) terminal command or from completing an uplink cancels all active alarms. When this is used to cancel alarms that require a bioscan sequence, the scans must still be completed, but enemies will not spawn.
In Rundown 004, S scans had a decreased scan time scaling with the amount of team members in the expedition, with 4 prisoners reducing the time to slightly longer than a standard team scan and with only one prisoner not having a scan time reduction at all. This made expeditions with S scans very difficult with less prisoners in the team, subsequently making solo runs impractical. This is effect was markedly reduced in Rundown 005.