As detailed in a blog post by the right-to-repair organization iFixit, helium atoms can wreak havoc on MEMS silicon chips. MEMS are microelectromechanical systems that are used for gyroscopes and accelerometers in phones, and helium atoms are small enough to mess up the way these systems function. Yet both Android and Apple phones use MEMS silicon for their devices, so why were only Apple phones affected?
The answer, it seems, is because Apple recently defected from traditional quartz-based clocks in its phones in favor of clocks that are also made of MEMS silicon. Given that clocks are the most critical device in any computer and are necessary to make the CPU function, their disruption with helium atoms is enough to crash the device.
No word on whether it caused Siri to speak in a very high voice.