1) Get out of the map. 2) Identify the areas that will kill you if you enter them. 3) Spawn a receiver node outside of the map. 4) Float the node above the floor of the "killing area." [floating it above allows you to create more portals in that channel. it's just more efficient] 5) Save the map and exit forge. 6) Reload the map and you will die upon entering the portal.
No, either Forge Discussion or Halo Discussion, probably Forge discussion now that I think about it. By the by, I'm pretty sure everyone with a nice shiny brain knows this.