After throwing and detonating, the Hallucigen gas grenade will emit a green gas that distorts vision. It will cause NPCs to begin to fire upon each other, regardless of whether or not they are shooting their own allies.
HalluciGen gas grenades are not randomly generated as loot. Instead, the HalluciGen gas canisters the Sole Survivor needs to craft at a chemistry station can only be found at HalluciGen, Inc., and are at a finite number of nine.
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