Kidneys are a filter system. The main job of the kidneys is to remove waste from the blood and return the cleaned blood back to the body. Each minute about one litre of blood ï­ one-fifth of all the blood pumped by the heart - enters the kidneys through the renal arteries.
The volume of helium in the balloon has been estimated as being able to lift a total load, including the balloon material and the structure beneath it, of 65 pounds (29 kg) at sea level and 48 pounds (22 kg) at 8,000 feet (2,400 m).
The air inside of the balloon has weight too. A cubic foot of air weighs .078125 pounds. A medium size balloon will hold 90,000 cubic feet of air and suddenly you have 7,031 pounds of air mass to contend with. This mass does not include such things as the aerodynamic load on the balloon, the weight of the balloon system itself, or the passengers and crew.