This paper describes a relatively simple probability quantitative risk analysis model to determine appropriate fire scenarios for car parking buildings. The approach introduces a dimensionless measurement defined as fire risk level by multiplying probability by consequence. For the development of fire scenarios for car parking buildings, the key variables for the fire risk analysis are identified as vehicle parking distribution probability and how vehicles then form clusters of neighbours, vehicle classification, vehicle fire involvement probability, and the severity of vehicle fires. The selection of clusters of neighbouring vehicles and whether all vehicles in the cluster catch fire has the probability to affect the fire risk level. An example analysis is performed where a simple two-row, 100 space parking model with a 75% vehicle occupancy and 0.90 tendency factor weighting is used to obtain the vehicle distribution probability combined with various data sourced from the literature. It is found from the example analysis that fire risk level is largely driven by the vehicle fire involvement probability such that a single vehicle fire presents the worst case scenario in terms of fire risk.