When a latex balloon is released, it rises to a height of approximately 28,000 feet, with the helium gas expanding as it rises. With temperatures dropping to minus 40 degrees at this altitude, the balloon freezes. As the helium continues to expand in the frozen balloon, the balloon undergoes "brittle fracturing" and ruptures into small slivers which scatter and fall to earth. A small percentage of balloons which are released will experience leaks from defects and will not rise high enough to freeze and burst. The distance they travel and their distribution will be determined by current prevailing winds.
Research indicates that if 10% of the balloons from a 500 balloon release were to fall into this category, the average distribution would be one balloon per 15 square mile area.