Apparently, helium can affect Apple Watches and iPhones and cause them to malfunction, so discovered Redditor u/harritaco.
The hospital that Harritaco works at was installing a new MRI machine, and he noticed that soon after, everyones Apple Watches and iPhones stopped working. MRIs use very powerful magnetic fields, and their superconductors are cooled by helium.
Apple is aware of this and even notes it in the iPhone user guide. It warns that “proximity to helium can impair functionality and that to recover, devices should be left to air out for a week or so in an environment far away from the rogue helium.”
But why? Harritaco speculates that it’s because these devices contain microelectromechanical systems (MEMS). These are tiny mechanical systems integrated into chips. They’re used for technology like the gyroscope and accelerometers. MEMS are contained in small cavities because they need to bend and flex. The cavities are either evacuated to create a vacuum or filled with a gas.
This means that the MEMS devices have a seal to plug the gap where the air was pumped out (or another gas pumped in). While those seals are able to keep most air constituents out, they’re permeable to the very tiniest molecules. In particular, both diatomic hydrogen and monatomic helium can permeate the seals.
Our guess is that a MEMS oscillator used to generate a clock signal for the phones is misbehaving after exposure to helium, hence the system-wide failure.