Helium is a natural, non-flammable, non-toxic gas. There is no ecological damage resulting from the use of helium. It can be used safely either inside or outside. However, helium is contained in heavy, pressurized cylinders.
NEVER DELIBERATELY INHALE HELIUM. IT IS AN ASPHIXIATE AND CAN CAUSE SUFFOCATION AND EVEN DEATH
Extending the float time of latex balloons - Hi Float
If helium is not available, all balloons can be filled with air and hung or strung. Balloons will last longer with air fill than with helium. Most foil balloons have tabs on the tops & bottoms of the balloons for hanging or stringing (with string/fishing line/ribbon). We also hang large 36" latex balloons from ceilings to give them the appearance of floating, but not the cost or hassle. We use double sided tape or balloon tape to do this. Balloon tape does a great job holding the stringing material in place.
Helium Chart: Please use our guide to help determine how much helium you may need for a balloon and the corresponding weight to hold the balloon in place: