From Dungeons of Dredmor Wiki

Damage: 2 + 1

Duration: 24 turns

Weak Poison Cloud creates a 2 square radius (3x3) cloud of poison gas. Any creature in this area when it is cast, or moving into the area will be poisoned and choked.

It is cast by the following monsters: Pumpkinn (5% chance), Unhealthful Golem (25% change on hit), or triggered by a Toxic Gas Sprayer Mine or Brimstone Cloudburster Mine trap. It is also the side-effect of a hit with a Poison Bottle Bolt.