There are two main types of quenches, and both are triggered by the red button. A customer of ours actually pushed his once, out of curiosity. And no, he was not 7 years old. This button is primarily for safety purposes. In some rare cases, clear signage is ignored and metal objects like mop buckets, oxygen tanks, etc. get sucked into the bore of the MRI. These are very difficult to remove while the magnet is at field. And, if a patient is somehow pinned inside, an emergency push of the quench button can be a lifesaver. The button artificially heats the magnet and starts the chain reaction described above.