Much like Civilian Extraction, they trigger at random occasions in random parts of the map, and the player is required to defuse them. The achievement/trophy Right of First Defusal requires the player to defuse five bombs in a single match.
When a bomb is planted, the players are warned by an on-screen warning, and an Atlas Strike Team comprised of two soldiers in singleplayer and three in co-op will appear in the area the bomb was set. The Atlas soldiers are invisible to zombies, so it is advised to shoot them as soon as possible in order to prevent further trouble. The Atlas soldiers use common weaponry (ranging from submachine guns to assault rifles), and an XS1 Goliath may even appear after a few gas bomb rounds. The last Atlas soldier killed will drop a Camouflage power-up lasting for ten seconds, which provides great help when defusing the bomb (camouflaged players are still visible to Atlas soldiers) Defusing a bomb requires ten seconds in co-op and five in singleplayer.
Each bomb round, Atlas will try to plant three bombs. If the bombs are not defused in time, the area that the bombs were in will be contaminated, similar to Toxic Zones in Infection, infecting the player and requiring them to use Decontamination Zones in order to be cured (although they will also be cured at the end of the round). If three bombs detonate, a Goliath Exo Zombie will appear the next round.