No matter how big or beautiful they are, all helium filled balloon eventually lose their lift. For untreated latex balloons, it only takes a day for them to fall, while some Mylar balloons float for weeks. Helium molecules leak out of the porous latex at a relatively rapid rate, while the impervious metallic skin of a Mylar balloon seals the helium inside. Mylar balloons usually lose their helium in a slow leak through their valves or seams. But all balloons can be reinflated if the balloon itself is undamaged.
Place the regulator on the helium bottle. Turn the valve on. Press the regulator nozzle to check the flow. Check the balloon for any obvious holes or other damage. Untie any ribbon or string from the balloon. If the neck has been clipped with a quick-clip, release the clip. If it has been knotted, untie the knot. If the knot is stiff, loosen it by pushing a pencil or paper clip into the knot to pry the knot open. Take care to avoid puncturing ot tearing the fragile latex.
Place the mouth of the balloon on the nozzle of the regulator. Support the body of the balloon with the other hand to prevent the regulator from blowing a hole in the side of the balloon neck. Gently push the regulator nozzle to release helium into the balloon. Stop and listen for the sound of any escaping gasses that could indicate a hole in the latex. Continue to inflate the balloon to its proper size.
Pinch balloon neck closed and remove the balloon from the regulator nozzle. Tie or clip balloon neck to seal it. Tie a ribbon or string around the neck.
Place Mylar regulator tip on helium bottle and turn valve on. Depress regulator button to check flow. Locate valve tab on Mylar balloon. Remove ribbon or string from valve tab of balloon. Gently place valve opening over regulator tip. Depress button on regulator. Slowly fill balloon with helium. Stop when a few wrinkles remain. Remove balloon from regulator.
Put a small amount of pressure on the balloon and listen for any helium escaping from a faulty self-seal valve or weak seams. If no helium escapes from the valve or seams, tie a ribbon on the valve and enjoy the balloon.
If helium escapes from the valve, twist the valve tab several times and seal with a quick clip, then add ribbon. If helium escapes from the seams, the balloon is dead and cannot be reinflated.
Latex balloons biodegrade very quickly, making them difficult to reuse. If the balloon is more than a day old or has been in direct sunlight, it may be too degraded to salvage. It is much more difficult to untie a used latex balloon than to tie a new one, so most professionals recommend replacing rather than reusing whenever possible.
Do not release Mylar balloons outside as they can cause problems with power lines and radar.