Helium for balloons: what it is, how to use it and what to avoid

Helium is a light, non-flammable noble gas that makes balloons float because it is lighter than air. A standard 12 inch balloon requires about 15 litres of helium and floats untreated on average 18 to 24 hours; a 36 inch giant requires 226 litres. You only use helium for designs that really need to float; garlands and installations are filled with air. For paid work, you obtain helium from a professional gas supplier in rental cylinders, and there are three golden rules: never inhale, never release balloons, and always anchor helium designs with a weight.

What is helium, and why do balloons float with it?

Helium is a noble gas, and that word immediately dispels the most important misconception: it is completely inert and therefore not flammable. A helium balloon cannot explode like the infamous hydrogen balloons of the past; the worst that a helium balloon can do is pop.

A balloon floats for a simple reason: helium is much lighter than air. Fill a balloon with enough helium to carry its own weight plus that of the latex or foil, and it will rise. That’s why larger balloons float more easily and for longer: more volume means more lift. And that’s why very small balloons don’t float at all: a 5 inch balloon or a modelling balloon simply has too little volume to lift its own weight, with no amount of helium.

How much helium does each balloon size need?

This is the official Sempertex Gas Capacity Chart, the table with which you calculate every helium job in advance:

Here’s how to calculate it: add up the litres of your design, and divide the contents of your gas cylinder (which is listed in cubic metres on the cylinder, 1 m³ is 1,000 litres) by what one balloon requires. A cylinder of 1 m³ therefore roughly gives 66 balloons of 12 inches, but barely 4 giants of 36 inches. That difference is immediately the most important pricing lesson from the table: a 36 inch balloon uses 15 times more helium than a 12 inch, and that’s something your quote should know.

When do you use helium, and when just air?

More often air than you think. The rule of thumb is simple: helium is only for designs that need to float freely. Balloon bouquets on a weight, floating ceiling decorations, that sort of thing. Everything else, and that’s the majority of modern decoration work, you fill with air: garlands, arches on frames, backdrops, organics, table centrepieces. Those are either hung or stood firmly, so helium adds nothing except cost.

That choice is also simply professional: helium is a finite resource and, as the table above shows, one of your biggest variable costs. Those who use air where they can and helium where they must create more competitively priced quotes and a more sustainable story, and the latter is increasingly important to more customers.

This is how your balloons float longer

Four things determine how long your helium work stays afloat:

• Treat latex with Hi-Float. A thin layer on the inside before inflating extends the float time by up to twenty times. For installations that need to last a night or a weekend, this is the standard. Only for latex; foil does not need it.
• Foil retains helium longer. Foil balloons float for days without treatment.
• Timing. Untreated latex should be inflated on the day itself, as close to the event as possible. With Hi-Float, it can be done the day before. Foil can be done days in advance.
• Temperature. Heat expands the helium and stresses the latex, cold causes balloons to temporarily shrink and hang lower. Both recover, but plan your transport accordingly and never leave helium work in a hot car.

What you avoid

• Never inhale helium. The funny voice displaces oxygen from your lungs and that is downright dangerous. Always use a pump or the tap of your bottle, never your mouth on a balloon full of helium.
• Never release balloons. Every released balloon ends up as litter. Why we do not support releases read here, including the nicer alternatives.
• No helium in small or modelling balloons. A 5 inch balloon or a 260 does not float, no matter how much helium you push in; that's just wasting gas. Small sizes are for air-filled work.
• Always anchor. Each floating design gets a weight, each helium balloon individually secured. Even indoors, because you need to be able to access it.
• Handle bottles safely. Upright, secured during transport, and stored in a ventilated place out of the sun.
• Do not waste helium. The most expensive habit in the industry: helium in designs that could just as well be done with air. Your margin and the environment will thank you.

Frequently asked questions