At the last trade show one of my pest control customers told me he had a few units that had been chewed from the inside. It turns out that when they sealed the house for rodent exclusion there were rats inside the plumbing and to try to escape, they climbed up the vent and attempted to chew through the Critter Quitter. However, we made these so that the internal component is chew proof, so they failed. Nevertheless, it proves the effectiveness of both rodent exclusion sealing and Critter Quitter resistance.