Poison Rush is a gear perk that makes you move faster while you are poisoned. It turns a bad moment into a chance to sprint out of a gas cloud, and it fits a poison-heavy build.
When a poison effect hits Dani, your movement speed goes up until it wears off. That helps you leave the cloud quickly or close distance on whoever threw it.
Wear the Hazmat Shoes or Heisenberg's Loafers in the feet slot. Gear perks are fixed to the piece of clothing that carries them, so you get this one by wearing that piece, not by unlocking it in a menu.
Pair it with Poison Protection or Strong Constitution so getting poisoned costs less health and does not blind you while you run.