Cooperative Personnel Services Firefighter (CPS) Practice Exam

As pressure increases, both the upper flammable limit (UFL) and the lower flammable limit (LFL) decrease. This phenomenon occurs because the relationship between pressure and the behavior of gases is governed by physical principles of gas behavior. When pressure rises, the density of the gas also increases, which contributes to a more efficient mixture of fuel and air. As the concentration of the mixture increases, the limits at which the fuel will ignite narrow, thus leading to a decrease in both the UFL and LFL. Consequently, the range of concentrations of a combustible substance that can ignite becomes smaller at higher pressures. Understanding this relationship is crucial for firefighting and safety protocols, as it informs how flammable gases behave under different environmental conditions, allowing responders to effectively assess risks during fire incidents.