Boomer Bile is a throwable item you can find randomly on any campaign in Left 4 Dead 2.

Zombies in this game will be attracted to the bile of a zombie called a Boomer. This bile can sometimes be found in a jar in any campaign, and used against the horde. When you toss this on to the ground, all common zombies will ignore everything else and run towards the area of effect of the bile. They will flail all around until the bile ends, and once it wears off, the common zombies will target you again.

Boomer Bile can also coat any infected. If a zombie is coated in boomer bile, all commons will target them and bully them until they die, or until the bile wears off. The Boomer zombie themself cannot coat anyone other than survivors.

Sounds simple enough, right? Nope. Before you even think of stealing a Bile Jar and immediately tossing it, read this guide.

Boomer Bile can randomly be found during gameplay. It doesn't matter which campaign you play, it will always show up at some point.

However, one campaign, Dark Carnival, is scarce with Boomer Bile. At most you would find 3 jars in total throughout the entire campaign. You usually find one in the first chapter, it could be in the back of a truck or next to ammo and other items. If you're super lucky, you will find a second one up ahead in chapter 1.

Chapters 2-4 will never have bile. Trust me, with a total of over 3k hours, I have never seen Boomer Bile show up during these chapters of Dark Carnival in any of my playthroughs. The finale, however, is guaranteed to have one before you go out on to the stage.

One of the uncommon zombies you will encounter during your playthoughs is a zombie in a hazmat suit. These guys have a chance of carrying a jar of Boomer Bile on them, dropping them on death. You can tell if they're carrying any bile if it's seen on their waist, or just sometimes the game will bug and it will just be moving with him under his feet.
Not all hazmat zombies will carry Boomer Bile.















On No Mercy, there are zero spawns of bile jars on any chapter. The only way you can obtain one is by killing the hazmat zombies in front of the hospital, which are limited. However, in that area, the hazmat zombies have an increased chance of carrying a bile jar, although it's still possible to leave without one.

Since the spawns of bile jars are inconsistent in other campaigns, I have screenshots of where you can almost always find boomer bile on Dark Carnival. Again, I only took screenshots for Dark Carnival because the spawns on other campaigns seem inconsistent, other than No Mercy.

Many campaigns have these segments where an endless horde will start and you are forced to run to the saferoom, or to an objective. Here's a list of sections that include gauntlets:

LEFT 4 DEAD 2 CAMPAIGNS

-Dead Center, Chapter 3. Starts once you shoot through the glass in the store, or open the emergency exit door. Ends once the alarm is shut off.
-The Passing, Chapter 2. Starts once the gate in the sewers is opened. It never ends until all survivors are in the saferoom and the saferoom door is closed.
-Dark Carnival, Chapters 2-4 In chapter 2, you have to open the gates to the Mary-Go-Round and run to turn it off. In chapter 3, you activate the Screaming Oak roller coaster and run to turn it off. In chapter 4, you open the gate to the arena and run to the saferoom.
-The Parish, Chapter 2. The survivors trigger an alarm from a military outpost and must run to turn it off.
-Cold Stream, Chapters 1-2. In chapter 1, the survivors must open a shelter which somehow alerts an endless horde until survivors enter the saferoom. In chapter 2, the survivors have to blow up a fence to clear a path, and must run to the saferoom.

There's also one horde specifically that feels almost endless ... that being the horde caused from lowering the bridge in Swamp Fever, chapter 3. It may feel like this is a gauntlet where you must run to the saferoom and ignore commons, but it isn't. The horde is just REALLY long. You can either defend, or just run.

The finale's for both The Parish and Cold Stream are also gauntlets.

LEFT 4 DEAD 1 CAMPAIGNS

-Death Toll, Chapter 4. The survivors use a forklift to clear the path and must run to the saferoom.
-Dead Air, Chapter 4. The survivors are forced to go through a rigged metal detector and must run to the saferoom.
-Blood Harvest, Chapters 3-4. In chapter 3, the survivors cause a train car to crash into a bridge, knocking it down. Survivors must run to the saferoom. In chapter 4, there's a section where you exit a building window, on to train tracks. Once a survivor even stands in the window, the endless horde starts. Survivors must run to the saferoom.

Now before you go playing L4D2, trying to use Boomer Bile during any of these events, read this information. Not all of these gauntlet sections require you to use Boomer Bile. Instead, you should use it during these events:

-Dead Center, Chapter 3.









-The Passing, Chapter 2.*










-Dark Carnival, Chapter 4.









Yes I know you can see the outlines of survivors. Shh.

-Cold Stream, Chapters 1-2.






Chapter 1








Chapter 2


-Death Toll, Chapter 4.*










-Dead Air, Chapter 4.*










-Blood Harvest, Chapters 3-4.






Chapter 3








Chapter 4


*May require two bile jars to complete safely.



Zombies will often times target the weakest survivors first. They get a high priority to drop kick an incapacitated survivor. Special Infected don't really care about incapacitated survivors. While survivors are down during a horde, and they aren't out of the way to save, toss a bile jar to the side and go revive them. The zombies will all run where you toss the bile, or to whatever zombie you toss it on. Never toss the bile jar on to incapacitated survivors. The infected will not attack the survivor but they will body block them. If it's a mob instead (a small horde), then don't bother tossing your bile jar. Use a pipebomb instead.


It may be true that there are less commons while a tank is active, but the life of one common can ruin everything. If you go through a gauntlet and you suddenly hear the tank music playing, look for the tank and toss the bile jar on to them, then just go about your business. Commons will soon horde the tank, blocking him from moving. The damage from the commons punting the tank will deal damage to him.


It's the end of the game and rescue is here. An endless horde will start and it absolutely will not stop at all until all survivors reach the rescue zone. I also literally mean this horde is ENDLESS. There are NO breaks between hordes during the very end of a finale. Tanks will also constantly spawn. You kill one, another one will immediately spawn. Just throw your Boomer Bile wherever, and run.


This does sound unclear, but there are times where you have to do an objective and you won't be able to defend yourself as easily. This includes the finale of Crash Course, when the generator shuts down during the battle. You will need someone or yourself to throw bile while someone--or yourself--runs over to the generator and turns it on.
You will also need it in the second chapter of The Sacrifice. There's a spot where you must walk up a large pile of gravel that forces you to walking speed. There's a timer that starts once you start climbing from a certain point, where crows will suddenly fly away and alert the horde. If a common comes up to you and slaps, you will be reduced to almost no movement speed. If you toss a bile jar to the side, then they will leave you alone and you can freely pass to the conveyor belt, and your friends will also thank you (maybe). Of course, construction worker zombies may ignore the bile, so watch out for them.

Unless if it's Versus mode, never toss a Boomer Bile on to a tank if there's no active horde or mob. You will cause extra commons to spawn and horde the tank, and soon the commons will become a major problem. They will either get in the way,trying to reach the tank, or they will start punting you when the bile wears off.


I don't know why you would ever toss Boomer Bile randomly to pick up a Molotov or a Pipebomb. Unless if you have extra bile jars, never randomly throw your Boomer Bile to replace it with another throwable. You will just cause random commons to spawn and soon annoy you if you don't kill all of them. Throwing one out to pick up another bile? That can be fine sometimes, but other players might want to snatch it. If you find another bile jar, don't be too shy to ask your teammates if any of them want one.


For the love of god, don't immediately toss your bile jar the second you pick it up when there's no events or anything. Boomer Bile is your best friend, don't throw it away ... that sounded weird.


You may think "hey, my teammate is coated in bile, maybe if I toss mine, they will ignore them!" You're wrong. Commons immediately take coated players and other commons as a higher priority. Unless if the bile jar does coat anyone, the commons will entirely ignore the bile and go for the player. Still, don't toss it to try and coat a bunch of commons and/or specials. They will die faster than you think. It's best to just keep your bile jar if one of your fellow teammates gets coated.

-The duration of tossed Boomer Bile is roughly around 20 seconds.

-Boomer Bile has no means of friendly fire. You cannot cover your teammates in bile by throwing a jar on to them. Although, why would you even try screwing over your teammates at all?

-Boomer Bile may drop differently depending on the campaign. Keep in mind the whole thing I mentioned about Dark Carnival's Boomer Bile drops.

-If tossed correctly, the Boomer Bile area of effect can be in a place where no AI nodes exist, causing all commons to just stand in one area and jump about.

-Special infected do not care about Boomer Bile if it doesn't cover anyone. Special infected will hit each other if they're covered in Boomer Bile. If a player is covered, specials will go after them, but not always. If you get in their way, they will target you.

-One uncommon infected is the construction worker. They are more resilient than a common and they will entirely ignore Boomer Bile unless if a player or an infected is covered.

This should be everything you need to know about the weird idea of tossing a jar filled with puke on to a bunch of aggressive flailing bois. Once you learn how to properly use this item, you'll realize how much of a game saver this item is. Many players you'll play with will love to see a player who knows how to use Boomer Bile correctly.

I did use a few images that were not mine, while in the screenshots I took, although very unlikely you saw them, I used mods to make the game look a bit better. I'm just gonna leave this here so I don't get yelled at.

Hazmat Zombie picture and Bile Jar photo came from the official Left 4 Dead wiki.
The bile jar model I used is the Pizza Party mod made by Ellie.
The color correction mod I used has been removed from the Steam Workshop.
The texture mod I used is the Left 4 Dead 2 HD Remaster mod made by ClipoDEL.
The lighting effect mod I used is the Cinematic Lighting Effects made by Red Schism.