One day, when Erik Wooldridge was installing some GE MRI Machines at Morris Hospital, he started getting calls claiming that cell phones and Apple Watches the building weren't working. At first, he thought the MRI machine must have generated some kind of EMP, but other medical devices and Android phones were all working fine. As it turns out, the MRI machine leaked about "90,000 L of gaseous He", and it seeped into electronic devices as tiny Helium atoms tend to do. Unlike Android manufacturers, Apple uses MEMs oscillators as clock generators in their newer phones, which are more susceptible to "small-molecule gas" than quartz clock generators. Interestingly, both Apple and the oscillator manufacturer were already aware of the issue, as rare and bizarre as it may be. The full story is on the iFixit blog, and its a fascinating read. But quartz oscillators have some problems. They don't keep time as well at high (and low) temperatures, and they're a relatively large component- 1x3 mm or so. In their quest for smaller and smaller hardware, Apple has recently started using MEMS timing oscillators from a specialized company called SiTime to replace quartz components. A MEMS accelerometer under an electron microscope at 50 micrometer resolution. Specifically, they're using the SiT512, 'the world's smallest, lowest power 32 kHz oscillator.' And if the MEMS device was susceptible to helium intrusion, that could be our culprit! A failing oscillator would match Erik's symptoms, which he reproduced in an experiment. "I placed an iPhone 8 Plus in a sealed bag and filled it with helium. This wasn't incredibly realistic, as the original iPhones would have been exposed to a much lower concentration, but it still supports the idea that helium can disable the device. In the video I leave the display on and running a stopwatch for the duration of the test. Around 8 minutes and 20 seconds in the phone locks up. Nothing crazy really happens. The clock just stops, and nothing else. The display did stay on though."