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).
Given a fixed weight balloon, the less dense the air is the hotter the balloon needs to be to be neutrally buoyant. The hotter the air around the balloon the hotter the balloon must be, the higher the balloon the hotter the balloon must be, the moister the air the hotter the balloon must be to be neutrally buoyant.