Cooperative Personnel Services Firefighter (CPS) Practice Exam

As the pressure of a flammable mixture increases, the ignition characteristics undergo significant changes. Specifically, both the flash point and the auto-ignition temperature tend to increase. The flash point, the lowest temperature at which a mixture can form an ignitable mixture in air, rises because higher pressures require a greater concentration of vapor to achieve ignition. Similarly, the auto-ignition temperature, which is the temperature at which a substance will ignite without an external ignition source, also increases under higher pressure conditions.

This phenomenon is attributed to the altered physical and chemical dynamics of the flammable mixture, where increased pressure elevates the energy state of the molecules involved. Thus, more energy (in the form of heat) is necessary for the mixture to ignite spontaneously.

By understanding this relationship, firefighters and hazardous materials responders can better assess the risks associated with various substances under different conditions, which is critical for safety during firefighting operations and while handling flammable materials.