Flamethrower

For the Flamethrower in Deus Ex: Invisible War, see Flamethrower (DX2). "A portable flamethrower that discards the old and highly dangerous backpack fuel delivery system in favor of pressurized canisters of napalm. Inexperienced agents will find that a flamethrower can be difficult to maneuver, however."

- description of Flamethrower

The flamethrower is a heavy skill weapon appearing in Deus Ex.

Background
"The canister is double-walled to minimize accidental detonation caused by stray bullets during a firefight."

- Sam Carter

Used in combat by various organizations in 2052.

By 2072 this flamethrower was replaced by a new model.

Game item
The Flamethrower is a powerful weapon as it instantly sets enemies on fire. Enemies on fire continuously take damage and run around helplessly. A single ignite on Untrained is enough to kill just about anything in the game except for very HP heavy enemies like Men in Black who require either two ignites or Advanced Heavy Weapons skill.

Unfortunately, while the flamethrower is very effective against some enemies, it's next to useless against others. It does next to no damage to robots and half damage to commandos. Furthermore, commandos cannot be set on fire, which means you would need one full canister of fuel and Advanced heavy weapons skill to kill just one commando.

It can be found very early in the game however - one of the NSF soldiers in tunnels under Castle Clinton wields it - and until commandos start to appear it will be extremely effective.

As it consumes 10 ammo a second, running out of ammo is easy and if you are not very good at saving ammo generally another weapon is a better choice for more long-term damage. Stop firing just after you know the enemy is dead, or ignite them and retreat, rinse and repeat.