The health consequences following an accident, a disaster, or a pollution spike are not easy to assess, as the necessary methods and tools are not always available. Several national and international organizations have developed toxicological reference values for the inhalation route. These reference values are designed to support the management of both accidental and non-accidental situations. Their development follows the same steps: determining the severity of the health effect to be considered, determining the exposure dose, and potentially applying safety factors. For toxicological reference values in accident scenarios, three levels of protection are typically established: against moderate health effects; against severe health effects; against fatal effects. Regardless of the nature of the situation, these values were developed for a single substance considered in isolation, whereas the population may be simultaneously exposed to multiple pollutants. This document presents the various types of existing toxicological reference values, their derivation, and their purpose. It is by no means an operational guide describing a method for making decisions in situations that the assessor may face. (R.A.)