In most models of human behavior in fire, pre-evacuation response receives less attention than the actual process of evacuation. However, delay in responding during this period is strongly associated with injury and fatality. This paper explains the selection, operation and evidence for features of a model of occupant response during the pre-evacuation stage in fires in residential buildings. The goal of the pre-evacuation response model is to determine the proportion of occupants leaving apartments (or rooms in non-apartment buildings) at each time step. The model is designed for a wide range of residential occupancies and, as part of a larger risk model, cannot detail all aspects of response. The model is constrained by lack of data, but operates within the limits of available evidence.