Helium is a non-flammable, colorless, odorless, non-toxic, asphyxiant gas that makes balloons float. Balloons filled with air do not float because air weighs more than helium. The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen. Air also has small amounts of lots of other gases, such as carbon dioxide, neon, and hydrogen. Helium weighs 0.1785 grams per litre and the atmospheric air we breathe weighs about 1.25 grams per litre.
Helium gas is not dangerous, except when it is stored in tanks under high pressure. These tanks under pressure can be extremely dangerous, even deadly, when it is misused or when tanks are incorrectly stored.
Tanks must always be stored upright below temperatures of 125°F or 52°C in ventilated dry areas away from sunlight. Tanks should also be stored away from flammable elements, heat sources, and away from high traffic areas in order to minimize the risk of cylinders falling over.
Cylinders stored in wet or damp conditions risk becoming rusted causing the metal tank to weaken and the cylinder to puncture. Helium cylinders are equipped with built-in rupture disk devices. If the tank ever does rupture, the cylinders will release the gas in a controlled manner, decreasing the chances of the cylinder bursting.
Helium cylinders should never be dragged or rolled and always be secured with chains or straps when transporting.
Helium cylinders are never to be opened without the nozzle attached and valves should never be shut without releasing the pressure in the nozzle. Valves should always remain closed when not in use.
When disposing of a helium cylinder it is very important to contact your local recycling program in your area.
Other safety hazards are inhaling helium and refilling helium cylinders by yourself. Although inhaling helium may be fun, it can cause personal injury or death.
Young children should never operate a cylinder or be left alone with a helium tank.