A toxic cloud is an uncommon stage hazard that, if walked into, deals heavy damage at steady intervals toward fighters.
In Super Smash Bros. Brawl, a toxic cloud appears in The Subspace Emissary. It appears in some of the cave areas and The Great Maze. When the character enters this toxic cloud, they will incur damage rapidly, at about 2% of damage per second. This toxic cloud can not KO the player, since it does not do any knockback, but it does make the character more vulnerable to enemy attacks. The player can temporarily clear the toxic cloud by hitting a red switch often situated near the cloud.