Do common infected return to areas of the level that have already been cleared out?

Based on my knowledge of the game's AI Director - who is responsible for spawning zombies - special zombies and hordes will come indefinitely. However, it wasn't made clear if common infected also load back in to the level after they've been killed.

For instance, in the second level of the Dead Center campaign The Streets if I were to kill all of the ambling common infected between the beginning safe room and the overpass' point-of-no-return could I then roam that section of the level with relative impunity from common infected?

Similarly, in the first level of the Death Toll campaign The Turnpike there aren't any points-of-no-return. If I killed all of the common infected could I explore that level freely?

  • As the answers might be different for each game, please only ask about one game at a time. Sep 27, 2019 at 16:22
  • 2
    The director behaves the same in both games, and the wikia article makes no attempt to differentiate the behavior in L4D and L4D2. I'll edit the post regardless.
    – PausePause
    Sep 27, 2019 at 16:27

2 Answers 2


After playing three different levels and testing this I can confirm that idle zombie do not repopulate parts of the level you have cleared out.

I tested this on these Left 4 Dead 2 levels:

  • The Parish - The Quarter

  • Death Toll - The Turnpike

  • Crash Course - The Alleys

Crash Course's The Alleys is notable for being an especially long level yet while backtracking I only encountered a one horde event. In fact, after testing I think special zombies do not respawn in areas you've cleared out either. I did not encounter hunters, chargers, boomers, or the like during my backtracking. I did re-encounter a witch I had previously navigated around which indicates that they do not despawn even when left alone.

While I performed my testing on Normal difficulty I think that this information will be especially useful for players playing on Expert. On one occasion I was able to modify my weapon with a laser sight but quickly had to replace after I ran out of ammunition. I knew I could safely return to areas I'd traversed and I was able to go back and upgrade my new weapon from the laser sight container I'd passed earlier.

Lastly, I'd like to point out that I occasionally had to fight an incoming horde of zombies regardless of where I was. Meaning that idling common infected stop spawning when backtracking, but horde events can still occur.

The only question I still want to test is what's the respawning behavior like on The Parish - Bridge finale gauntlet event. I still want to know if the zombies do not stop spawning while on the bridge and if I could return to the safe room if I truly needed to, in the same way I could during the previous levels.

  • 1
    While idle zombies don't repopulate, the AI director may start a horde on you if it decides you're taking too long.
    – Powerlord
    Nov 18, 2019 at 22:04
  • I just updated the second-to-last paragraph to better articulate that point.
    – PausePause
    Nov 18, 2019 at 22:20

It seems to depend on the map, maybe even the area within the map.

I have doubled back before on the first stage of No Mercy, and not seen any respawned zombies. But in Death Toll, in the stage that begins in the bell tower, I have stood up there sniping zombies for a half hour or more, and I keep seeing more. It's a big place, so I suppose it's possible I had simply hadn't noticed them earlier, but I doubt it.

I am interested to know as well if anyone has more concrete evidence.

  • Thanks for the answer. I'm going hold off on accepting until I get something concrete. As for the bit on Death Toll bell tower, the Director will spawn idling zombies in sets of 30 after there are fewer than five left. That's probably why you kept seeing more. It doesn't clarify if they would stop spawning if you traversed the area though.
    – PausePause
    Sep 30, 2019 at 20:14
  • How do you double back in The Apartments? Part of the level, if I recall correctly, requires dropping through a hole in the floor. I thought that was a point of no return.
    – PausePause
    Nov 18, 2019 at 21:41
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    You're right, but there's quite a bit of the level beyond that. I have doubled back from the end safe room, looking for throwables, pills, or medkits.
    – Ryan_L
    Nov 18, 2019 at 22:18

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