Filling with air is done with the mouth, with a manual or electric inflator (such as a hand pump) or a source of compressed air.
When rubber balloons are filled with helium so that they float they can hold their lift for only a short time depending on the size of the balloon, the time can vary from 18 hours to several days. The enclosed helium atoms escape through small pores in the latex which are larger than the helium atoms. Balloons filled with air can hold their size and shape much longer.
Even a perfect rubber membrane eventually loses the gas to the
outside. The process by which a substance or solute migrates from
a region of high concentration, through a barrier or membrane,
to a region of lower concentration is called diffusion. The inside
of balloons can be treated with a special gel (e.g. "Hi Float"
brand) which coats the inside of the balloon to reduce the helium
leakage, thus increasing float time to a week or longer. Latex
rubber balloons are completely biodegradable.
Metallized nylon animal-shaped balloonsBeginning in the late 1970s,
some more expensive (and longer-lasting) foil balloons have been
made of thin, unstretchable, less permeable metallized plastic
films. These balloons have attractive shiny reflective surfaces
and are often printed with colour pictures and patterns for gifts
and parties. The most important attributes of metallized nylon
for balloons are its light weight, increasing buoyancy and its
ability to keep the helium gas from escaping for several weeks.
However, there has been some environmental concern, since the
metallized nylon does not biodegrade or shred as a rubber balloon
does, and a helium balloon released into the atmosphere can travel
a long way before finally bursting or deflating. Release of these
types of balloons into the atmosphere is considered harmful to
the environment. This type of balloon can also conduct electricity
on its surface and released foil balloons can become entangled
in powerlines and cause power outages.