This paper provides a survey of the recent literature about firing costs and discusses the transmission channels of firing costs in a partial equilibrium context. In addition, we expand our analysis two types of firing costs in a New Keynesian model with purely endogenous separations. We further distinguish between the effects resulting from respecting and non-respecting the bonding critique. We find that the two types of firing costs do not show significant differences. However, respecting the bonding critique enhances the overall performance of the model.