PPS is the term used to describe the death of a hermit crab that happens early on, more specifically a few days after you have bought it. PPS is only possible because of the fact that hermit crabs are captured from the wild (since they cannot be bred in captivity without extreme measures being taken) and do not ship well. In order to possibly prevent a premature death it is imperative to have an isolation tank and check the temperature/humidity gauges of the store you are buying from. Therefore you can recreate the environment the hermit crab came from. You can slowly increase the temperature and humidity to what it is to your main tank during the stay in the iso tank. They should be allowed to relax for at least 1 week in the iso preferably two. No handling, and only going in to change the water and food. Only allow one inch to an inch and a half of substrate. No burrowing should happen if it can be helped for the sake of them needing to be observed. After a week they can be introduced to the tank after being introduced to everyone in a neutral area.
To Read more on PPS go here, it’s where I learned everything: http://crabstreetjournal.com/xoops/modules/news/article.php?storyid=165&keywords=Post+purchase+stress