Barrel

A flotilla of barrels on MAP32: Caribbean

Burning barrels on MAP23: Barrels o' Fun

The exploding barrel is a relatively common hazard found throughout many Doom levels; a cylindric metal barrel containing what appears to be green slime or "nukage". Barrels form part of the "dangerous Doom environment" described in the game booklets:

Exploding barrels: Scattered around the base are drums containing toxic waste. If your shots hit one of these barrels, it's kablooey time! It might take several bullets to set off a barrel, but a single blast of any of the other weapons usually does the trick.

A barrel takes damage like a monster, and when its hit points reach zero, it explodes, accompanied by the sound effect DSBAREXP. The explosion inflicts damage to all objects within the blast radius of 128 units, including monsters, players, and even other barrels (exploding one barrel in a closely-arranged cluster of barrels often leads to a chain reaction of explosions). Each barrel starts with 20 hit points, which is the same as the Trooper.

A useful tactic, sometimes called a "barrel frag", is to wait until one or more enemies are close to a barrel, and then shoot the barrel to detonate it (this tip is given in the user manuals). Barrels are extremely effective and efficient weapons when used correctly: a well-timed chain reaction can produce thousands of hit points of damage from a single shotgun blast, for example.

Damage inflicted by an exploding barrel was long thought to be simply attributed to whoever last damaged it caused it to blow up -monster or player-, but after a more recent analysis of the source code this turned out not to be that simple. A barrel's map object doesn't get its 'inflictor' field set when it's actually exploding but only when it's damaged without exploding, therefore monsters or players that destroy barrels in a single attack do not cause the barrel's explosion to be attributed to them, and thus cannot cause infighting or be attributed a kill as a result of it.

E.g. if a monster A damages a barrel WITHOUT making it explode, and then a monster B damages it further and makes it blow up and hurting both itself and monster A, then monster B will start chasing after monster A, because the barrel survived one hit from monster A and thus A was registered as the damage's inflicter.

This trick can be used to trigger monster infighting even between monsters of the same species, e.g. between two imps. Their fireballs still do no damage, but once they get into melee range they will claw each other to death. However, this is harder than it sounds to achieve in practice because a barrel must survive at least one hit from a monster in order to result in infighting when exploding, otherwise the monsters are damaged but do not start infighting.

In versions v1.1 and older of Doom, the above infighting trick could also result in a monster to attack itself if it was damaged by its own barrel blast, resulting in the so called barrel suicide.

Doom II added the burning barrel. However, these are just animated obstacles. They do not explode or inflict damage in any way (except in Brutal Doom, as seen below).

Heretic's pods and Hexen's mushrooms play the same role as Doom's exploding barrels. Strife also has exploding barrels.

Barrel data
Thing type	2035 (decimal), 7F3 (hex)
Appears in	Shareware Doom Registered Doom Ultimate Doom Doom II/Final Doom
Hit points	20
Radius	10
Height	56
Mass	100
Speed	0
Sprite	BAR1 (normal) BEXP (exploding)
Class	Obstacle

Burning barrel data
Thing type	70 (decimal), 46 (hex)
Appears in	Doom II/Final Doom
Radius	10
Sprite	FCAN
Class	Obstacle

Notes

Before barrels are crushed.

Aftermath of barrels that were crushed.

• The barrel animation frames is incorrectly set in the game. The first two frames are the animation of the slime inside the barrel, while the next five frames are the barrel exploding. However the first three frames should be used for the slime animation, and the fourth frame seems to be intended to be a flinching animation.
• Interestingly, when a barrel is destroyed by a crushing ceiling, before it can complete its explosion animation, it leaves behind a pool of blood and flesh. See also a demo of the phenomenon below.
• The burning barrel also exists in The Ultimate Doom version of the engine; however, its sprites are not correctly offset and it is never used.
• The Doom 64 barrels are largely unchanged from their original portrayel, though they appear wider in appearance.  They are just as explosive as before, with the one lone change being that it takes an extra half second to explode after taking enough damage.
• There are a lot of barrels in Barrels o' Fun.
• In Brutal Doom, both barrel types are heavily tweaked: explosive ones have slightly more hit points and explode more elaborated and violently when destroyed, dealing much more damage to everything near it. After acquiring a berserk pack (or a demonic strength rune), the marine can easily pick up and throw explosive barrels at enemies (or drop them harmlessly on the ground by pressing the alternate fire key); burning ones now emit very realistic-looking flames, and the marine, starting on version 0.19, can kick and flip them over to set nearby enemies on fire, damaging or even killing them without ammo usage.

Demo

• A level demonstrating how an exploding barrel can leave bloody remains when crushed (file info). It features several such barrels placed under a crushing ceiling; walk over the silver touchplate to see the effect.

Sources

• Doom Oddities thread at the Doomworld forums
• Unofficial Doom Specs v1.666, section 4.2.6.2
• Barrel glitches thread at the Doomworld forums
• BARREL.WAD A demo map allowing a player to experiment with different barrel damage patterns and discover which ones do and which ones don't cause infighting.

See also

• Barrel explosions which do no damage
• Barrel suicide