It takes only five seconds for a worker who is walking on moving grain to become engulfed in it to the extent that he is unable to extricate himself. It only takes 60 seconds for him to become completely submerged.
Moving grain acts like "quicksand" that can bury a worker before he has time to react. "Bridged" grain and vertical piles of stored grain can also collapse unexpectedly if a worker stands on or near it. The behavior and weight of the grain make it extremely difficult for a worker to get out of it without assistance.