The Hazard Switch is a new option in Super Smash Flash 2 that allows you to turn off pretty much any dangerous or otherwise significant environmental hazard on all stages. It can be easily accessed in the match options menu.
Whether it’s by a lot or a little, removing hazards will change how you play.
It affects each stage in a different way, but in general you’re going to be focusing a bit more on direct combat with your opponents when you turn hazards off. It all depends on what you’re looking for, really.