THORNTON, Colo. -- The family of a 12-year-old boy says he was hurt by a weather balloon that fell from the sky Tuesday afternoon and landed on the campus of Niver Creek Middle School in Thornton.

The 12-year-old student said he saw the balloon fall and ran over to see what it was and when he picked it up he received an electric shock.

School administrators brought the balloon into the school. Not knowing what it was initially, they called the fire department.

School officials soon realized, reading a label on the balloon that read, "This is a harmless weather instrument" and "Property of the National Weather Service" that the device was part of a weather balloon.

The fire department confirmed that it was a National Weather Service balloon and transported the boy to a nearby hospital as a precaution.

The boy had complained of numbness in his hands but is now OK, said the boy's father, Bill Bunney.

National Weather Service spokesman Byron Lewis said in his 30 years with the NWS he has never heard of anyone being injured by a weather balloon.

The weather balloon is made up of two parts -- typically a large latex balloon, attached to an instrument called a radiosonde -- a device that measures the temperature and moisture content of the atmosphere. There is a small battery inside that radiosonde that powers the instrument so it could send information back to the National Weather Service.

The school claims that the battery was really hot or overheated and may have caused the shock to the boy.

The NWS said the radiosondes are packed in Styrofoam and the battery is usually dead after four hours and should not have been hot.

It's not clear where this balloon comes from but this weather balloon was most likely launched in the morning so there was plenty time for the battery to expire, Lewis said.

The NWS has several launching points across the country and launches the balloons twice a day -- early in the morning and in the evening.

In Denver, the balloons are launched at Stapleton Airport at 5 a.m. and 5 p.m. during Daylight Saving Time. All weather balloons are launched at the same time across the country, so the balloons would be launched at 7 a.m. in the east coast and 4 a.m. in the west coast.

The balloons are also launched in two other cities across the state.

The school said the radiosonde also emitted a foul sulphur-like odor. On its Web site, the National Weather Service said, "The instrument is powered by a water-soaked battery (generating 15 to 18 volts) that uses a chemical containing sulfur. If the battery is still active when you find the radiosonde it may be warm to the touch and give off a strong odor for up to several more hours. Keep the instrument outside and wait until the battery has cooled off before removing it." The NWS said on its Web site that if you find a radiosonde, mail them back to the National Weather Service so they can be recycled.

Additional Resources:

Learn more information about radiosondes, go to the National Weather Service Web site