Toxic Gas is a hazard found in Super Mario 64 and Super Mario 64 DS. It is found in Hazy Maze Cave (specifically in the Toxic Maze) and functions very similarly to Poison Water. If Yoshi, Mario, Luigi, or Wario fall in it, they will slowly lose health and if they don't get out, they die. It is best to limit the time you spend in the Toxic Gas. If you are under the effects of the Vanish Cap, the Metal Cap, or the Mega Mushroom, you will be able to walk through the Toxic Gas without an issue.
In Super Mario 64 DS, the color of the Toxic Gas was changed from yellow to purple. Also unlike the original, instead of slowly chipping away health as you're in it, you will be stopped as you take damage (in the same way as touching an enemy). Additionally, if the Health Meter is low, the "low air" sound effect will play while in it. Toxic Gas is also seen in Goomboss Battle surrounding the course.
Trivia
- Toxic Gas is the only hazard from Super Mario 64 to change how it affects the player in the remake, in the sense that characters are now stopped whenever they take damage in it.