Can be crafted at a Chemistry station using:
N.B. This crafting recipe will only appear if you have a HalluciGen gas canister in your inventory. You do not need the Demolition Expert perk to make these.
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.
Some enemies are unaffected by the gas, as the game will indicate with a "<Name> is too powerful for this effect." notification.