> The superconducting magnet in an MRI scanner is always on even when not performing a scan.

This should be placed on the entrance with big bold letters, I think that a lot of accidents could be avoided by simply providing "WHY" information. I had MRI scan and I wasn't aware that machine was active even when not performing scan and now after knowing that I think that personnel there was very lax with allowing me to enter the room after instructing me to put metal objects away AND without enough emphasis how dangerous it could be if I forgot to do so.