The Flamer and Heavy Flamer are flamethrower-type weapons that project an ignited stream of prometheum fuel over a wide area, igniting many enemies in a single shot. Flamers are infantry support weapons, given usually by officers to their most courageous soldiers as a sort of honor, but most troopers carry these with disdain due to the range of the weapon.

Heavy Flamers are larger versions of the weapon with two nozzles, producing a deadlier inferno. They are often used by specialists in dense conditions, such as jungle warfare, or Terminators, who make good use of them in cramped ship-boarding actions. Sisters of Battle of the Adepta Sororitas often carry Heavy Flamers in their squads. Heavy Flamers are also seen mounted on armored vehicles as secondary weapons, although the Sisters of Battle use twin-linked Heavy Flamers as primary weapons on the Immolator tank.

More powerful Flamer-type weapons, Inferno Cannons, are available to the Imperial Guard mounted and mounted on the Warhound Titan.

A form of the heavy flamer, known as the Incinerator, is used by the Inquisition, primarily the Ordo Malleus (Daemonhunters). These weapons are fueled by the purest consecrated prometheum, and, like Psycannons, are useful against supernatural forces. These weapons are among the most effective in the imperial arsenal, forgoing the enemy's heretical armor, their cowardly cover, and their warp-spawned magics.