Although I’ve never done it I know a little bit about rescuing someone from one. There is a rescue tube that is assembled from three (or four?) pieces that nestle for more compact storage. Assemble them on scene, & lower it around the person. Now grain between the person & the tube can be removed, this allows them to breathe easier if they were up to their chest. Next you can get a harness around them & pull them up & out. Like any other confined space rescues, the rescuer(s) should be harnessed & roped so they can be pull out if they get into difficulty