343 Guilty Spark introduces himself to John-117 upon the initiation of containment protocol on Installation 04.

Containment protocol is a series of protocols designed to assist a Monitor to enforce the containment of the Flood parasite in the various Flood containment facilities.


When the containment-protocol is activated, the main objective is to destroy all species that have sufficient biomass to sustain the Flood, by activating the Halo rings. Sentinel and Enforcer drones must be deployed to engage what Flood forces have managed to escape and keep them contained within the facility. If containment is breached, then emergency measures must be taken to ensure that the situation returns to stability.

The protocol also includes the procedures involved in activating the Halo Array. It requires a Reclaimer to retrieve an Index for activation, that the Monitor store the Index within its own data arrays for transport, and that only the Reclaimer can use the Index to activate the system, because the Monitor is not able to activate Halo by itself.[1]

There are different procedures about enforcing this protocol, judged by the size of the outbreak. If the outbreak is a minor one, then, the monitor must deploy a few Sentinels and constructors to make the needed procedures, but if it is a major outbreak, like the outbreak seen on Quarantine Zone, Major Sentinels and Enforcer drones will be mass deployed to eradicate all Flood and its vectors. Containment-protocol is normally enforced by Monitors, but there have been cases of Sentinels taking it upon themselves to enforce containment.

The leadership of a Monitor is important, but not always necessary. The Sentinels and Enforcers of Delta Halo continued to enforce containment even after their monitor, 2401 Penitent Tangent, was captured by the Gravemind,[2][3] and despite their lack of a Monitor the Sentinels of Onyx abide by containment-protocol by neutralizing local infection vectors - the UNSC Marines, Spartan-III's and the Covenant forces on or near the planet.[4]


When Flood outbreak appears imminent, the containment-protocol becomes the principal priority. This is the reason that the monitor makes simulations of this event.

When enforcing this protocol, the Monitor must:

  • Determine what, how, and where the problem is.
  • Initiate the Installation's Sentinel manufacturing facility to deploy Sentinels, Constructors, and Enforcers, depending on the severity of the outbreak, to eradicate any Flood infection vectors and perform necessary maintenance.
  • If the outbreak cannot be contained, or it looks likely that the Flood will escape, the Monitor will seek out an individual known as a Reclaimer, teleport that Reclaimer to the Library and have it retrieve the Index for activation.
  • Once the Index has been retrieved, the monitor must store it internally to prevent it falling into the hands of the Flood, and teleport itself and the Reclaimer to the Control Room to activate Halo.

Here, the containment-protocol presumably finishes and the Halo Array is activated. If the firing is stopped for some reason, (Delta Halo for example) the Monitor must restart the containment-protocol or activate the rings through the Ark.



  1. Halo: Combat Evolved, level Two Betrayals - 343 Guilty Spark: "Protocol does not permit units of my classification to perform a task as important as the reunification of the Index with the Core. That final step is reserved for you, Reclaimer."
  2. Halo 2, level Sacred Icon
  3. Halo 2, level Quarantine Zone
  4. Halo: Ghosts of Onyx
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