Inhibitors are usually hidden in GRE containers. If you’re near one such container, your GRE Access Key will help you find it (lower left corner of the screen). You will also hear a voice that says: “inhibitor container detected” or “inhibitor container nearby.” If you’re less than 10 meters away, you’ll see the container’s location marker pop up on the screen.

• GRE Quarantines: The inhibitor crates are hidden inside a building full of Infected.
  
• GRE Anomalies: The inhibitor is next to a Special Infected. You have to take down the monster first.
  
• Military Airdrops: Usually (and inconveniently) on top of very high buildings.
  
• Metro Stations: They tend to appear in stations after powering them.
  
• Random locations: Some of them are just sitting inside a pretty ordinary building, waiting to be discovered. These crates are the hardest to find.
  
• GRE Quarantines: The Inhibitor crates are hidden inside a building full of Infected.
  
• GRE Anomalies: The Inhibitor is next to a special Infected. You have to take down the monster first.
  
• Military airdrops: Usually (and inconveniently) on top of very high buildings.
  
• Metro stations: They tend to appear in stations after powering them.
  
• Random locations: Some of them are just sitting inside a pretty ordinary building, waiting to be discovered. These crates are the hardest to find.

Originally posted by author:

To get the first six Inhibitors and unlock the feature, simply play through the main questline. You will get the first three from Hakon right after an incident at the Bazaar, and the second during the Markers of Plague quest. From that moment onwards, you’re free to look for them yourself

Originally posted by author:

****Old Villedor - North****

• 1. Jump on the balcony, then find the room with the hole in the roof. You’ll come across this location during The Only Way Out (2x)
  
• 2. Top floor, next to rooftop opening. You’ll see it during Unruly Brother (2x) 
  
• 3. Reach the door using the suspension bridge, then open the door on your left. Part of The Raid quest (2x) 
  
• 4. Near the top of the water tower (2x)
  
• 5. In the building south of the Bandit Camp. You’ll also come across it during The Raid quest (3x) 
  
• 6. GRE Anomaly (2x)
  
• 7. Inside the GRE Quarantine building (4x)
  
• 8. Inside the GRE Quarantine building (4x)
  
• 9. In the Hayward Square Metro Station, after unlocking it. It’s near your bed (1x)
  
• 10. Inside the green GRE container, go through the roof opening (1x)
  
• 11. Inside the Nightrunner’s Hideout (big building with the pillars). It’s inside the safe on the ground floor. The code is 1-0-1 (1x)
  
• 12. In military airdrop THB-04B (1x)
  
• 13. Inside the Dark Hollow building (1x)
  
• 14. Top floor of an ordinary building (3x)
  
• 15. On the second highest floor (1x)
  
• 16. There’s a side quest called ‘The First Biomarker’ in this location. You’ll get the inhibitor for completing it (1x)

Originally posted by author:

****Old Villedor - South****

• 1. GRE Anomaly (2x)
  
• 2. GRE Anomaly (2x)
  
• 3. Next to the bridge, in the water (1x)
  
• 4. In the metro station, just go downstairs (1x)

Originally posted by author:

****Central loop - North****

• 1. Inside Metro Station Downtown Court, not far from the entrance (2x)
  
• 2. Inside the Electrical Station (2x)
  
• 3. Inside the Newalls Crossing Metro Station. Find it in the bathroom next to your bed after powering the station (1x)
  
• 4. Top of a high building. You’ll see it during the Orders quest (2x)
  
• 5. Highest floor of a smaller flat, it has open doors on both sides (1x)
  
• 6. Just north of the giant VNC tower. It’s inside a green military transport container in front of the tower’s entrance (1x)
  
• 7. GRE Quarantine building (4x)
  
• 8. GRE Quarantine building (4x)
  
• 9. GRE Anomaly (2x)
  
• 10. There are three different inhibitor containers in this location. The first is in a safe in the Downtown Thugs bandit camp (code is 3-1-3), the second is in the Military Airdrop on the roof, and the third is just a bit further to the north in a small container on one of the red platforms (3x)
  
• 11. Near the bed in the Waterside Metro Station (1x)
  
• 12. GRE Anomaly (2x)
  
• 13. GRE Quarantine building (4x)
  
• 14. Next to bed in the King William Bridge Metro Station (1x)
  
• 15. Inside the Saint Paul Electrical Station (1x)
  
• 16. GRE Anomaly (2x)
  
• 17. GRE Anomaly (2x)
  
• 18. Inside the Dark Hollow (1x)
  
• 19. GRE Anomaly (2x)
  
• 20. Inside the high building just north of the Fish Eye Canteen (1x)

Originally posted by author:

****Central Loop - South****

• 1. GRE Quarantine building (4x)
  
• 2. GRE Anomaly (2x)
  
• 3. Next to bed in the Cathedral Metro Station (1x)
  
• 4. In the South Loop Metro Station (1x)
  
• 5. GRE Anomaly (2x)
  
• 6. GRE Anomaly and another one right below the bridge (3x)
  
• 7. In the VNC Tower Metro Station (1x)
  
• 8. GRE Anomaly. You have to cross the river to find this one. Follow the question mark (2x)
  
• 9. In the water (1x)
  
• 10. In a safe in the Electrical Station, code is 3-1-4 (1x)
  
• 11. Military Airdrop THB-UT0. You’ll come near it during the Broadcast quest (1x)