Left 4 Dead 2 Easy Way to Kill a Witch

"Boomer, don't let it puke on you."

―Zoey

"They've been calling those Boomers. For obvious reasons."

―Rochelle

The Boomer is an extremely bloated Special Infected. Their mutation has caused them to produce immense quantities of bile which they attempt to vomit on the Survivors, temporarily blinding them and summoning a small Horde. Though fragile and slow, the Boomer can be dangerous to a Survivor team whose health or combat abilities are compromised.

The Boomer's role in Left 4 Dead and Left 4 Dead 2 is to slow down, blind and sow general confusion among Survivors, giving the Hordes of Infected of any species openings to mount attacks with higher probabilities than normal to achieve damaging results. The known presence of a Boomer may also cause Survivors to spread out a little (to avoid being coated in bile) and this too works to the advantage of Special Infected such as Smokers or Jockeys when mounting a coordinated attack. Without other infected, the Boomer's low health and extremely low damage makes him entirely powerless, because he's an easy target at range.

The Boomer is voiced by Fred Tatasciore.

Appearance

In both games, the male Boomer has short black hair and wears a navy blue shirt and brown pants, both stained with sweat and puke and stretched to breaking point around the Boomer's enormous gut. When idle, the Boomer makes loud burping and gurgling noises which change to loud groans when it sees a Survivor.

Extent of Mutations

The Boomer has undergone extreme external and internal mutations by some adverse reaction to the Infection. The most notable observation of the Boomer is their extremely bloated belly, most likely caused by their stomach (and possibly most, if not all of their gastrointestinal system) being hijacked by the Infection to overproduce bile in massive amounts. The sheer tension on their skin and organs has resulted in a breakdown of the epidermal and dermal layers, causing the skin to become thin and fragile. In some places, the skin has even ruptured, exposing some of the bile-filled internal organs. This enormous buildup of internal pressure makes the Boomer quite vulnerable to any outside agitation, as even the slightest gunshot wound or melee shove will result in the Boomer violently exploding, sending blood and bile everywhere — hence the name, and the extremely low health. Even so, the Boomer can autonomously engage in strenuous self-directed physical activities (e.g. jumping down from a height) without injury.

Other physical mutations observed include massive boil-like growths that appeared upon their skin and face. Whether this is due to overproduction of bile is unknown. Similar to the other Special Infected, they are not distracted by high frequency noises such as pipe bombs or car alarms going off.

The Boomer's bile has a unique chemical binding effect with Infected and/or non-Infected flesh which produces an extracellular stimulus. This chemical stimulus induces a pheromone-like attraction from nearby Common Infected which causes them to swarm and attack the bile-saturated source. The exact nature as to why this induces a negative response is unknown but the response is non-discriminatory between Infected and non-Infected flesh (i.e. using a Boomer Bile vial on The Tank triggers the same violent response against the Tank). It should be noted that typically Common Infected have been known to exhibit an extremely basic form of logic (hence their ability to recognize non-infected). The bile-flesh response seems to trump this logic, which could mean that the stimulus is extremely intoxicating for the Common Infected.

Left 4 Dead 2

As with all the original Special Infected, the male Boomer reappears in Left 4 Dead 2 and has received a slight change of appearance. His skin tone is more fleshy, he has shorter hair, and has a few more boils. Though when compared to his Left 4 Dead counterpart, he seems more wrinkly and "deflated", and his skin seems to be breaking out in several spots. The greatest change in the Boomer's appearance, however, is the addition of a female counterpart.

CEDA has shown some interest in the Boomer, hoping to utilize their unique abilities to their gain. A wall chart detailing their appearance and abilities appears early on in Dead Center, and Infected Hazmat-clad CEDA operatives can be found carrying vials of treated Boomer bile. The said Boomer Bile is basically a Pipe Bomb that doesn't blow up and still has limited duration, but it may also cause the enemies hit to be targeted by other infected.

Female Boomer

The Female Boomer (or "Boomette") is seen wearing a dark blue or black tank top and blue jean shorts, drenched in bile. Her hair is light blonde and parted back behind her head. Unlike the male Boomer, she doesn't have boils or growths. Instead, her flabby flesh shows signs of fungus growth, and perhaps highly Infected forms of tinea around her shins. The skin on her hands and wrists appears blackened from necrosis, similar to gangrene.

Her eyelids and the skin in the area around her eyes are also black. Her teeth seem to be heavily misshapen and worn down, either meaning she either lacked proper dental hygiene before she became Infected, or her constant puking has broken down the enamel in her teeth (or possibly a combination of both). She makes higher-pitched gurgling noises as compared to the male Boomer, and sounds more pig-like.

In terms of gameplay, she functions exactly the same as the male Boomer.

Abilities

The Boomer's primary attack is to launch a stream of vomit which can hit multiple Survivors that are close to him. If he is killed, he will explode, causing Survivors (and Infected) close to them to stagger and spraying Survivors with bile. Survivors hit by Boomer bile will have their vision obscured (losing outlines of their teammates as well) and while the bile is not deadly in itself, will instantly attract a Horde to attack them, as well as any individual Common Infected who happen to be in the area. They will glow yellow to teammates and purple to the Infected.

Multiple Survivors hit by Boomer bile will not each attract a Horde to them; the one Horde will instead attack all of them. This is also true of Survivors who are covered in bile by the Boomer's death after the Boomer has used their vomit attack; a second Horde will not be attracted until the effect has worn off upon the Survivor's first hit, and until the Boomer themselves attacks again. The Boomer may vomit on incapacitated Survivors and on those who have been pinned by other Infected. Boomer bile, at least that issuing from the Boomer itself, has no effect upon other Infected. The Boomer may also claw the Survivors to do 2 points of damage on Normal.

Attacks

Left 4 Dead

Types	Weapon	Damage	Properties	Cooldown
Primary Attack	Bile	N/A	Will cover hit Survivors in bile, blinding them and attracting a Horde (also spawns a certain amount of Common Infected, about 20). You can also get additional range with this when aiming slightly up.	Between pukes: 30 sec. (Plus additional 2 sec for the puke. Cooldown starts after you stopped puking.) Blindness of Survivors: 15 sec.
Secondary Attack	Claw	4	Hitting Survivors who are currently occupied with something (e.x. helping up other Survivors) will get their action canceled.	1 attack per second. You can also attack while stumbling, even if you are currently not in the ego-perspective.
Special Attack	Bile Explosion	N/A	If the Boomer dies, he releases a bile explosion, covering every Survivor around him in bile and shoving everyone back (this includes teammates and will result in stumbling for 1 second).	N/A

Left 4 Dead 2

Types	Weapon	Damage	Properties	Cooldown
Primary Attack	Bile	N/A	Will cover hit Survivors in bile, blinding them and attracting a Horde (also spawns a certain amount of Common Infected, about 20). You can also get additional range with this when aiming slightly up.	Between pukes: 30 seconds (plus additional 2 sec for the puke. Cooldown starts after you stopped puking.) Blindness of Survivors: 15 sec.
Secondary Attack	Claw	4, 20 (Expert)	Hitting Survivors who are currently occupied with something (e.x. helping up other Survivors) will get their action canceled. Filling in gas tanks counts as occupation.	1 attack per second. You can also attack while stumbling, even if you are currently not in the ego-perspective
Special Attack	Bile Explosion	N/A	If the Boomer dies, they release a Bile Explosion, covering every Survivor around them in bile and shoving everyone back (this includes teammates and will result in stumbling for 3 seconds).	N/A

Note: Information still needed for some areas.

Tactics

Survivors

Like The Tank and Charger, parts of the Boomer may stick out from walls and obstacles. As the Boomer has low health, a few shots should take care of them. AI Boomers tend to make this mistake far more often compared to Tanks or Chargers, even if they are able to move (AI Special Infected only start moving when a Survivor "enters" its area).
When a Boomer spots a player, they will make a surprised sound (male) or loud groaning (female). When in puking range of a player, the sounds are changed. On Easy and Normal, you'll have enough time to shove or get away from the Boomer before they puke on you. On Advanced and Expert, they'll puke immediately, so if you are up close, immediately shove them. Running away will not work, as they can arc their puke to hit Survivors from a fair distance.
After a Boomer dies, they will release bile and an accompanying explosion. The bile will soak players within the exploding range. Anything near to the Boomer when they died will also be stumbled, friend or foe. This can be used to stumble Tanks, but it's often rare to see these Special Infected together.
- Be wary of this, as both AI and human-controlled Boomers use the explosion for many creative means. The explosion stumbles human players which makes them susceptible to Special Infected attacks, or in ledges such as The Coaster and The Hotel, cause Survivors to start hanging on for dear life and results in less guns against the Infected.
- The explosion also stumbles the Witch, who will then go after the person who killed the Boomer. It also sends nearby dropped items flying, such as supplies into inaccessible or not normally explored areas, so either search for them or press on if this happens.
- Using your explosion to knock away items specifically is a good idea. For example, if there is a tank incoming, you could die near a molotov to send it flying, or in The Atrium, you could suicide near gas cans to make them flying around the small map. Together with The Spitter's ability to burn gas cans, you can cause chaos and panic.
Try to be fairly spread apart but within close range of other Survivors when a Boomer is near. If all Survivors get biled, at once the Horde can easily decimate an unprepared group in seconds on harder difficulties and makes it harder for the team to help each other.
If any Boomers spawn, they should be taken care of immediately as a Horde on Expert can be extremely excruciating in terms of gameplay checkpoints then any other Special Infected, even more so then the Tank. If the two appear at once, kill the Boomer first, as having a Tank along with a Horde chasing after a player is extremely dangerous.
- Be careful if the Boomer is near an Alarmed Car, as a Boomer's explosion can still trigger the alarm and summon a Horde anyway. Instead, wait for the Boomer to move far enough away that their blast radius won't be an issue, or if you have an accurate ranged weapon and are in a large enough area of the map, kill the Boomer from a distance that won't trigger the alarm.
Boomers can go kamikaze by dropping off of high areas to explode themselves and bile nearby Survivors. Watch out for them as it can result in a surprise Horde.
If you jump while you're very close to an exploding Boomer, if you will not get stumbled. You can use this method to prevent you or another survivor to hang on a ledge when a Boomer explodes.
While biled, the auras of nearby items and players are disabled, similar to Realism Mode.
To counter the effects of bile, you can do the following things:
- Go to a corner and take out your melee weapon. Make sure your allies are close enough to protect you but not too close for your melee weapon to hit them. Whenever Infected appear on your screen, swing your melee weapon to kill them. To help identify enemies, using commands can help you tell who is a friend or foe while biled.
  - Alternatively, a one-entry area or a chokepoint works just as fine as the Infected are funneled into one area, allowing you to shoot accurately.
- Throw a Molotov on your feet. You may want to take Pain Pills or an Adrenaline Shot before doing so, as the fire can easily take out chunks of your health rapidly on harder difficulties. This will kill the swarming Infected, but should only be used if you cannot break free from the Horde.
- Throwing a Pipe Bomb is effective for a short amount of time, as the Infected will chase after the pipe bomb until it explodes. This of course, will not affect the Worker Infected, as they wear earmuffs, making them immune to the Pipe Bomb's beeping.
Survivor Bots can detect Boomers from a distance and easily take care of them, so if you have trouble finding a Boomer, let the Bots do the work for you.
After a Survivor Bot is biled by a Boomer, they will start meleeing in random directions, so be prepared to get the incoming Infected off them, especially in Left 4 Dead 2 due to melee fatigue.
Bots do not shoot Boomers up close, although when biled, they will shoot the Boomer, but only by accident.
Encountering a Boomer can actually be good news, as a single survivor can shoot it at close range and get biled on purpose, summoning with this a controlled Horde when they're prepared against it and relying on their still dry teammates to help them fend it off. This is very useful for clearing areas that are heavily populated by lesser Infected. In addition, it resets the next Horde timer, giving the survivors a longer time threshold until the next AI Director Horde is spawned.

Infected

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"The Boomer was designed to distract, injure and frustrate the Survivors with several surprise waves of Infected hordes, as well as break the "shoot everything that moves" mentality. While the other Infected are attackers alone, the Boomer plays a highly valuable supporting role."

While playing as the Boomer, one must keep in mind that one is playing a support class. They serve as the initiator of ambushes, the one who starts panic. While playing as the Boomer, avoid charging in with ravenous Hordes to inflict underwhelming damage with melee. Instead, puke on Survivors from unseen locations, wait for teammates to start an ambush, and jump in at hectic moments to explode and cause increased confusion.

A Boomer hides in attempt to surprise the Survivors in the early stages of the game's development

Instead of engaging Survivors directly, wait for them to come to you. Sometimes it is more effective to wait around a corner and let them come into puking range. This is because there is a delay between a Boomer stopping its movement and puking. Play it safe and let them come.
- Players may also accidentally react and shoot you without backing away, covering them in bile.
The Boomer makes very distinctive sounds, making it easy to determine when and often where a Boomer has spawned. To reduce the chance of being killed prematurely, spawn immediately before vomiting, somewhere close to where all of the Survivors are grouped together, preferably while the Survivors are distracted with other Infected or actions (such as healing).
Once a Boomer has vomited on the Survivors, whether or not it has actually hit anyone, there are two options: use the kamikaze method, or run, hide, and recover.
- The most basic kamikaze method a Boomer can use involves walking up to the Survivors after vomiting on them and clawing them. This will often result in one of the Survivors shooting the Boomer, causing it to explode on the nearby Survivors.
  - Pros:
    - Causes a bit more damage
    - Causes victims in the Boomer's blast radius to stumble, leaving them temporarily helpless
      - Allows Common Infected to deal extra damage
      - Prevents Survivors from escaping Spitter acid or fire
      - Prevents Survivors from freeing other Survivors being pinned by other Special Infected
      - May knock survivors off a ledge, instantly incapacitating them
      - May slow down fleeing Survivors, allowing pursuers (Tank, Witch, etc.) to catch up and deal significant damage
    - May cover missed targets with bile
    - Re-cover victims already covered in bile, extending how long they are blinded and how long they attract zombies
    - May send nearby items (such as supplies or gas cans) flying away from Survivors
      - Gas cans necessary for Scavenge Mode, The Atrium finale, or The Port finale will have to be retrieved, causing delays that allow other infected to respawn or attack
      - Aforementioned necessary gas cans may be launched to unreachable places, such as off a rooftop, forcing Survivors to destroy the can and wait for it to respawn
  - Cons:
    - Leaves the Infected a man short
      - You may not get another boomer for the next attack, it depends on luck
    - Easily countered if Survivors shove you back to a safe distance
    - May cause a Special Infected to stumble
      - Makes it easier for Survivors to kill them
      - May save a Survivor from death or incapacitation
      - May knock Special Infected off ledges to their death
      - May knock Special Infected into fire
- A variation to the kamikaze method is to stand in an area above where the Survivors will pass later. Jump down into the middle of the group and the Survivors will most likely kill you. The resulting bile attracts the Horde and makes it easier for other Infected players to deal damage due to the confusion caused. A Boomer can also light themselves on fire, and then explode all over them before they realize it was even there. However, this is not recommended for new players, as the Survivors might take a longer time than anticipated to reach the area player, resulting in your death.
- The final trick is to stand next to an alarmed car facing the Survivors. They will most likely open fire, killing the player but also hitting the car and summoning a Horde. Do note that Survivors need to be close enough to a car to trigger the alarm; bullets fired from far away won't do.
  - This method can be applied to the Witch as well. Once the Witch has been startled, the Infected team should attack to create even more chaos and to prevent the Witch from being killed before incapacitating someone.
- Alternatively, the Boomer can flee after puking, let their bile recharge, and puke again later. This allows the Boomer to recharge their bile while the Survivors are currently dealing with the panic you caused. Some Hordes last longer than the time it takes the bile to recharge, allowing you to pull off the combos in quick succession and can be used to buy your teammates more time. However, since you are still a part of the field, you will be making a lot of noise, which will keep Survivors aware of your presence. To counteract this, hide in locations they wouldn't expect to see a Boomer or in the Infected-only areas. If you can get enough distance between you and the Survivors, you can get the game to prompt you with the "Press E/X to move closer to the Survivors" message, which will bring you right back to them in Ghost Mode, allowing you to have the perks of respawning without having to die.
  - However, Boomer bile has the longest recharge of any Special Infected ability, meaning that the Infected will be short one person for the duration of the bile recharge period. It is actually faster to kill oneself and respawn than it is to wait for the bile to recharge.
To generate additional Infected, you must either explode on a non-purple Survivor or wait until all Survivors are no longer surrounded by a purple aura and then strike again.
Another tactic that many experienced players use in gameplay is a maneuver called a Rocket Boomer, in which the player is in spawn mode and they climb to an elevated surface, then they run toward the edge at the Survivors, and while in mid-air, they spawn and land in the center of the Survivors' group.
- Infected can accumulate significant speed while in spawn mode, and spawning mid-air allows players to maintain their momentum.
Work with other Special Infected to maximize damage and confusion during an attack.
- Boomed Survivors will have difficulty killing Special Infected that are attacking other Survivors
  - Boomer Bile impairs vision
    - Survivors may not see distant players that are pinned by Special Infected
    - Survivors can't see outlines, so they won't see Survivors that are pinned by Special Infected that are out of their line of sight, such as behind a wall
  - Boomer Bile draws infected
    - Hits from Common Infected will cause Survivors to flinch, drastically lowering their accuracy
    - Hits from Common Infected, as well as the Common Infected's bodies themselves, will impede Survivor movement, preventing them from reaching Survivors that are in trouble or escaping Spitter acid if they are spat upon
- Common Infected drawn by Boomer Bile can deal extra damage to helpless Survivors being attacked by Special Infected
- Exploding near a Special Infected who is pinning a player can cause them to stumble, freeing the Special Infected and giving them the opportunity to attack someone else or escape and attack later
  - Using this strategy with the Hunter or Charger is particularly effective, as they become able to attack again very quickly after releasing a pinned Survivor
If The Tank spawns, having a Boomer slime even one Survivor is a huge bonus. The Tank will cause a lot of confusion, but if he is assisted by a wave of regular Infected, the Survivors can get overwhelmed quickly.
There is a delay between the activation of a bile attack and a Survivor being coated. If the Survivor kills or shoves the Boomer, the bile will disappear in mid-flight, leaving the Survivor clean.
The Boomer should almost always attempt to cover an incapacitated Survivor with bile. If you can, try to vomit on downed Survivors so that the Horde attacks them. The Infected will prevent them from being revived, and attacks from Common Infected will do a significant amount of damage to downed Survivors (5x damage on Versus).
There is a maximum distance the vomit can go before disappearing into thin air. If it's from too high of a vantage point, the bile will never hit the Survivors.
Don't hide right next to thin walls. Not only can Survivors shoot through most of them, but your ample mass may stick through (due to vector errors), giving them a free kill. The slime from the aftermath will, unfortunately, be unable to get through. Try to hide slightly off the wall to minimize cheap kills.
Players soaked in bile may shoot their teammates by accident due to their impaired vision. If an entire group gets biled, than they may shoot or hit each other, causing extra damage as well as confusion.
The Boomer will have an easier time vomiting on Survivors if they are in an enclosed space, so attacking players inside a small room is a good choice.

Boomer Tips and Tricks Gameplay

Here is a video with a lot of helpful information and tactics for the Boomer, courtesy of Criken2.

Achievements

Survivors

	BLIND LUCK	(20G)
	You or another Survivor take no damage after being vomited on by a Boomer.

	CLEAN KILL	(10G)
	Shove a Boomer and then kill him without him splashing on anyone.

	OUTBREAK
	Catch a rare strain of Infection, then pass it on to someone else.

Infected

Left 4 Dead

	BARF BAGGED	(20G)
	Cover four Survivors with Boomer bile at once.

Left 4 Dead 2

PC exclusive

	FAT NINJA
	As the Boomer, vomit on a Survivor without having direct line of sight with them.

Behind the Scenes

In the Developer Commentary, it's mentioned that originally the Boomer's explosion simply caused damage to nearby players, and that the Horde-attracting abilities were assigned to the Screamer, another Special Infected that was cut from the final game. When the Screamer was dropped, the screams that formerly attracted the Horde were changed to the Boomer's bile. The Boomer's old explosion behavior can be seen in this video at 1:57:

When the Boomer's bile was first added to the game, it was red. It later was replaced by the green seen in the final version.

Notes

The Boomer was the first Special Infected ever conceived.

A very rare glitch will cause a Boomer to die without exploding. Bile will still cover any Survivors too close.
When the Boomer explodes or vomits, the bile does not appear on the ground. This fits in, because otherwise the Horde would always be attracted to the site of a Boomer death. As it stands, the Horde is only summoned when the bile comes into contact with a Survivor. It is possible that the Survivor's natural pheromones combined with the bile produces a scent that is strong enough to attract a Horde of large size. Strangely, in Left 4 Dead 2, when a Bile bomb is thrown, it attracts a Horde, regardless of whether it hits an Infected or not. It may have been treated with pheromones by CEDA beforehand.
When the Boomer explodes, the arms disappear, possibly due to them being blown to bits. If the Boomer's explosion is enough to destroy their arms as well as break glass and destroy wooden doors, it would more than likely do at least some damage to the Survivors.
- However, if one uses the command "z_Boomer_gibs 1", they can find bits of flesh, both arms, and the upper jaw of the Boomer among the bloody mess. The following commands "map MAPNAME" and "sv_cheats 1" need to be used beforehand because "z_boomer_gibs 1" has "game cheat" marked on it.
Judging by the weight and immensity of the Boomer, their body should have been able to restrict the Boomer from jumping higher than a foot or climb ladders, since the stress/tension would cause the Boomer's internals to strain and explode. However, for gameplay purposes, Boomers are given as much freedom as their Common Infected counterparts.
- Though judging by how the Boomer explodes, it might be air or the bile instead of weight.
When examining the Boomer's navel, players can see the Boomer's intestines protruding from it.
A Boomer was apparently hit by a police car at the beginning of the Death Toll campaign, as a pair of Boomer legs are laying against the police car. This may be the reason for the large amount of dead bodies lying around the same area as if a Horde were summoned.
- In the ported Left 4 Dead 2 version of this campaign, the Boomer's body is no longer there.

Two *Boomers* surrounded by a crowd of Common Infected in the Zombie Survival Guide video

Although large, pus-filled sacs are covering one of its eyes, it still has full vision, as seen in Versus, probably for gameplay reasons.
The Boomer is the only Special Infected other than the Tank to undergo changes in physical appearance upon dying. For example, the Boomer's lower body only remains after exploding. In addition, the Tank's skin texture changes if he takes fire damage from Molotovs or Incendiary Ammo, for example. However, none of the other Special Infected undergo any form of physical change upon death.
Along with the Witch, Jockey, Spitter, Hunter from Left 4 Dead 2, and the Tank found only in The Sacrifice, the Boomer is not wearing shoes. He is, however, wearing socks.
The female Boomer is referred to as "Boomette" in its model files. Currently, the Boomer is the only Special Infected to have both male and female models, and the first to have more than one model in general (The Witch being second and the Tank being third).
When playing as the female Boomer in Versus, the first-person view shows arms with boils, like the male Boomer has. As seen from third-person view, she does not have these boils, instead having blackened skin on her hands and slightly up her wrists that seems to have been caused by necrosis.
Normally, dead bodies tend to bloat, and when cut into, release gas. Though the Boomer is not a traditional "dead" zombie, this may be an allusion.
In the Dead Center campaign, down the first set of stairs is a conference room: to the left is a poster board with pictures and graphs labeled "Boomer". The Boomer in the pictures are from Left 4 Dead and not the remodeled version. This suggests that CEDA named the Boomer. The Survivors from the first game may have picked up on this somehow, or it may be just coincidence that the two groups would choose to use the same name. This may be how the Survivors from Left 4 Dead 2 learned the Boomer's name, although it is still referred to through nicknames the Survivors give them for the first two levels.
- Although rare, in the Dead Center campaign's first two levels, Ellis may occasionally refer to the Boomer by its proper name.
The Left 4 Dead 2 male Boomer seems to have a bite mark on the back of his head, suggesting that he has gotten the Infection from it.
In the Left 4 Dead 2 Strategy Guide, It shows the male Boomer's Left 4 Dead design instead of his new one in his description.
When the Boomer pukes on other Special Infected, nothing happens to them, but when the Special Infected are hit with a jar containing Boomer Bile, they will have obscured vision (as seen in Versus) and the Horde will attack them.
For unknown reasons, female Boomers do not appear in Dead Center, The Passing, Hard Rain, The Sacrifice, or the ported Left 4 Dead campaigns.
- Additionally, female Boomers have a much higher chance of appearing on the Swamp Fever and Cold Stream campaigns, even appearing more frequently than the male.
An interesting note about Boomer bile in Left 4 Dead and Left 4 Dead 2 is that if puked on, one only needs to set their character to idle and quickly resume playing and their screen will no longer be covered in bile. However, you will still be covered in bile and therefore still attract a Horde.
- Note that this only works in Offline Co-op and Matchmaking.
Sometimes the game glitches causing a voice switch: A female Boomer may have a male Boomer voice or vice versa.
Biologically speaking, the liver creates bile. If that is the same "bile" that the Boomer releases, it raises the question if the Infection increases the size of their liver and/or their production of bile.
Boomers are the only Special Infected to not spawn during the Mutation "Last Man on Earth", since there are no Common Infected to be attracted to their bile, thus rendering them useless.
When an AI Boomer spawns on a greater height, they will strangely fall down, exploding like a Kamikaze, though if there were any Infected Ladders, they would ignore it.
The chances for a female Boomer being spawned in the map can be altered by the player using these two console commands;
- z_allow_female_boomer — This value must be set to 1 (if 0, female Boomers will never spawn, thus, ignoring the console command below.
- z_female_boomer_spawn_chance — (decimal number between 0 and 1) Set the percentage chance for a female Boomer to appear.
The Boomer is the only Special Infected that has captions given to them when they fall down from a distance. Other Special Infected do not receive this.
Boomers likely come from obese victims of the Infection. Not only does the Boomer's bloated appearance support this, but also the fact that the liver produces bile for the body to absorb fat, as well as other nutrients. A high food intake may be a stimulus that caused the Boomer's mass production of bile.
The boomer still explodes even if the gore is low.
Both the Versus and Realism Versus icon in Left 4 Dead 2 shows Coach facing off against a L4D1 rendition of the Boomer.
If a survivor is being grabbed by a Special Infected (Smoker, Hunter, Charger or Jockey) and a Boomer is close to them, bots will automatically shoot it in order to free the survivor, trading a summoning of a Horde for assuring they can at least defend themselves.

Gallery

See image archive for more images…

Trivia

The Boomer is the only Special Infected to have a gender variation, even though it was developed in the second game.
The Boomer, along with the Tank, Hunter, Smoker, and Witch make cameo appearances in the 2012 horror movie The Cabin in the Woods, along with other horror characters from both cinema and gaming.
The Boomer is similar to the Bloated Butcher from the 1997 video game Blood.

References

The Infected
Playable
Introduced in Left 4 Dead				Introduced in Left 4 Dead 2

The Boomer	The Hunter	The Smoker	The Tank	The Charger	The Jockey	The Spitter
Non-Playable
Introduced in Left 4 Dead				Introduced in Left 4 Dead 2		Cut Infected

The Witch		Common Infected		Uncommon Infected		The Screamer