As fog cloud, but in addition to obscuring sight, the solid fog is so thick that any creature attempting to move through it progresses at one-tenth normal speed, and all melee attack and melee damage rolls suffer a –2 penalty. The vapors prevent effective ranged weapon attacks (except for magic rays and the like). A creature or object that falls into solid fog is slowed, so that each 10 feet of vapor that the creature or objects passes through reduces falling damage by 1d6.
Unlike normal fog, only a severe wind (31+ mph) disperses these vapors, and it does so in 1 round.