The helium inside a party balloon eventually leaks out and can escape Earth into space permanently — yet almost all of our usable supply has to be recovered from underground gas fields, and the same finite element is needed to keep most MRI magnets cold enough to operate

A party balloon might be the only object in an average house capable of leaving the planet for good.

Helium atoms are small and slippery enough to squeeze between the polymer chains of latex, which is why the birthday balloon is sulking on the floor by Tuesday. Once out, it mixes into the atmosphere, and over time some reaches the upper atmosphere, where helium ions can escape into space. A steady fraction of it then leaves altogether.

Very few everyday purchases end that way.

How the planet makes it

Slowly, and by accident. Nearly all terrestrial helium is a by-product of radioactive decay, as uranium and thorium in granite basement rock shed alpha particles, and an alpha particle that picks up two stray electrons is a helium atom. Accumulating that gas into anything worth drilling takes geological time. The U.S. Geological Survey files helium among the nonrenewable resources, drawn from the subsurface and not replaced on any timescale that matters to a hospital.

Most of what forms is lost on the way up. Helium has the smallest atomic radius of any element, so it threads through pore spaces that hold methane without trouble, and useful accumulations require unusually effective seals, often salt or anhydrite. Commercial recovery generally needs a gas stream running at least 0.3 per cent helium. Assessing the American resource, the Survey found 1,217 reservoirs clearing that bar, of which the 481 with complete enough records came to roughly 2 per cent of the reservoirs in significant gas fields.

Why none of it comes back

Earth sheds roughly 50 grams of helium every second. David Catling and Kevin Zahnle, writing in Scientific American, traced that loss to the polar wind, where open magnetic field lines near the poles let light ions accelerate out into space. That one process carries off nearly all the helium the planet loses, running at about the rate the rocks leak it back.

Air sits at 5.2 parts per million helium and stays there. Recovering it from the atmosphere is possible in a laboratory and ludicrous in a factory, since separating a few parts per million from the air costs far more energy than tapping a reservoir where geology has done the concentrating already.

The magnets that drink it

An MRI scanner images tissue because its coils are superconducting, and they are superconducting because they sit a few degrees above absolute zero.

Only helium stays liquid down there. The agency’s 2025 minerals summary is blunt about the consequence: nothing substitutes for helium in cryogenic work below roughly minus 256 degrees Celsius.

A conventional scanner holds up to 1,700 litres of liquid helium, according to Philips. If the magnet quenches, meaning superconductivity fails and the coolant boils, that helium vents through a pipe in the roof and is gone. Routine shutdowns and top-ups claim a share as well.

USGS figures for 2024 put MRI at 17 per cent of American helium use. Lifting gas, meaning balloons and airships, took 18. Semiconductors, fibre optics and controlled atmospheres accounted for another 15, welding 8, and deep-sea diving 5.

Recycling barely features. The same survey notes that helium in large-volume applications is seldom recovered domestically, aside from some liquid boil-off systems, and that reuse is more common elsewhere in the world. Balloon gas is the same element that cools the magnet, only less pure, and once it lets go there is no second pass at it.

Sealed magnets and a sold reserve

Engineering is catching up on one side of that ledger. Philips has shipped a fully sealed 1.5 tesla magnet since 2018 that takes a one-off charge of seven litres and keeps it for life, quench included, with around 2,000 installed and more than six million litres saved by the company’s count. Siemens Healthineers has its own sealed magnet, cutting a 1.5 tesla scanner’s charge to 0.7 litres from as much as 1,500, with no quench pipe needed. Many older scanners will remain in service for years, while newer sealed designs can cut helium use dramatically.

Supply has moved in the other direction. Washington entered the helium business in 1925 to float military airships and left it in 2024, when the Bureau of Land Management sent $460 million from the sale of the Federal Helium System, Cliffside field and 680 kilometres of pipeline included, to the Treasury. Messer, an industrial gas company, owns it now.

That leaves a short producer list dominated by the United States, Qatar, Russia and Algeria, with smaller volumes out of Canada, China and Poland, and European Union buyers barred from Russian helium since September 2024. The base price for Grade-A helium ran to about $14 per cubic metre in 2024, before the surcharges producers add on top.

Decay will keep restocking the cupboard on a schedule measured in hundreds of millions of years, indifferent to anyone’s procurement cycle. Everything else is a decision: which fields get drilled, which magnets get replaced, who sells to whom, and how many litres go up through a roof vent because a machine bought fifteen years ago still takes excellent pictures. A handful of countries hold the taps. The next shortage will not be geology’s fault.