What happens to balloons filled with helium if you let them go outdoors?
It will go up higher and higher, where the atmosphere isn’t as thick, and the helium becomes less compressed and expands. This stretches out the balloon until the balloon eventually pops. Once this happens, the remnants of the balloon fall back to earth, where it becomes litter.
Moral of the story; Balloon releases are littering.
They’ll continue to rise, the helium inside the balloon will expand as the pressure decrease with altitude until eventually the balloon ruptures.