Forest fires represent a growing safety concern since their frequency is increasing, with severe damages to humans, environment and structures. The present work focuses on the impact of forest fires on a particular type of target: liquefied petroleum gas (LPG) tanks. A computational fluid dynamic (CFD) model was applied to simulate the response of LPG tanks of different sizes exposed to a forest fire scenario. Results are presented in terms of pressurization rates, temperature distributions and velocity fields focusing on the effects of the tank size variation on the vessel response. In particular, it is pointed out how the tank diameter greatly affects the pressurization rate, but it as a negligible effect on the wall temperature distribution. The outcomes of this work provide useful results to evaluate the possible failure conditions, thus supporting the emergency response to wildland fires.