Barrel

The exploding barrel is quite common throughout the Doom levels. 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.

Doom II added the burning barrel. However, these are just animated obstacles. They do not explode or inflict damage in any way.

Heretic has large floating spiky green spheres which play the same role as Doom's exploding barrels.