Smoke

Toxic Gas is a rare stage hazard appearing in Super Mario 64, Super Mario 64 DS, and Super Smash Bros. Brawl. When the character walks into an area of toxic gas, he/she will start to take damage at steady intervals.

In Super Mario 64 and Super Mario 64 DS, Toxic Gas appeared only in the Toxic Maze in Hazy Maze Cave. The gas covered most of the ground in the Toxic Maze. When Mario, Luigi, Wario, or Yoshi entered an area of gas, they would lose one wedge of health on their health meter after several seconds. If one of them stayed in too long, he would lose all of his health and die. Metal Mario/Metal Wario was not affected by toxic gas, however.

In Super Smash Bros. Brawl, Toxic Gas appears in the Subspace Emissary. It appears in some of the cave areas and the Great Maze. When the character enters this toxic gas, he/she will incur damage at a much faster rate than in Super Mario 64/Super Mario 64 DS, at about 2% of damage per second. This toxic gas could not KO the player, since it does not do any knockback, but it does make the character more vulnerable to enemy attacks. The character could temporarily clear toxic gas by hitting a red switch often situated near the toxic gas.

Trivia

 * In Super Mario 64, if Mario stays in Toxic Gas for a period of time without moving, he will start to cough.