What happens to balloons that float off into space?

After helium filled balloons escape, or are released, they rise up into the atmosphere at around two metres per second. They will rise to about 28,000 feet (8.5 kilometres) in about 90 minutes. The pressure and temperature both drop as the altitude increases; the temperature at this height is a very cool minus 40°C.

By now the balloon has reached its elastic limits and, at about 700% of its original un-inflated size, it bursts. The shatter that happens in these conditions is referred to as a “brittle fracture.” This shattering effect is similar to the smashing of glass, and the balloon splinters into many tiny pieces, about the size of a 5- or 10-cent piece, and then floats back to the ground, spreading over a large area.

Of course, the best way to keep our environment clean is to be careful how you dispose of your balloons after you have finished with them. This includes not releasing them into the air if they are helium filled, and to cut the balloons at the knot, deflate the balloons then place the deflated balloons in the bin.