Description of the issue from the original thread [0]:<p>The processor in a modern, high volume device typically has its main clock driven by what's known as a MEMS oscillator. These are barely visible mechanical systems that resonate at some designed frequency, and include packaging to convert this resonance into a useful electrical clock signal. These devices are extraordinarily cheap ways to produce a steady clock, but they have a number of drawbacks. Most relevant, in order for these types of devices to function properly, the mechanical resonator must be inside a tiny hermetically sealed chamber with either a controlled gas inside or a vacuum, as the gas composition in the chamber can affect the output frequency.<p>For both cost and physics reasons, these hermetic seals are not perfect, and are somewhat commonly permeable to small atomic gasses such as helium.<p>...<p>For this specific case, Apple devices probably share a common family of MEMS resonator to reduce manufacturing costs. This clock likely leaks in helium rich atmospheres, pushing the output frequency outside of the bounds that the main processors are designed to handle, rendering them non-functional. If left idle long enough, the devices may begin to function again, but depending on the concentration of helium which leaked in, this could take anywhere from weeks to years to occur in natural atmosphere and temperatures.<p>[0] <a href="https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabled_every_ios_device_in_facility/e7g5rcw/" rel="nofollow">https://www.reddit.com/r/sysadmin/comments/9mk2o7/mri_disabl...</a>