Which two environmental factors can cause the flammable range to vary considerably?

Which two environmental factors can cause the flammable range to vary considerably?

• A. Heat conduction and convection ratio
• B. The heat of combustion and the Heat Release Rate (HRR)
• C. Temperature and pressure
• D. Pyrolysis and vaporization rates

Answer: (C)

Flammable range is determined by how much fuel vapor is present in the air and how much oxygen is available to support ignition. Temperature directly affects vapor formation. When the surroundings are warmer, more fuel evaporates into the air, so you can reach ignition with a smaller vapor concentration (lower LEL) and the mixture can remain ignitable over a broader range as vapor generation changes. Pressure also matters because it changes how readily a liquid fuel will vaporize. Higher ambient pressure tends to suppress vapor formation, reducing the amount of fuel vapor in the air and shifting the range, while lower pressure allows more vapor to form, expanding the range. Because both temperature and pressure alter how much fuel vapor is present, they can cause the flammable range to vary considerably. Other factors listed relate more to how heat is transferred or how energy is released, rather than environmental conditions that change how much fuel vapor is in the air for ignition.

Flammable range is determined by how much fuel vapor is present in the air and how much oxygen is available to support ignition. Temperature directly affects vapor formation. When the surroundings are warmer, more fuel evaporates into the air, so you can reach ignition with a smaller vapor concentration (lower LEL) and the mixture can remain ignitable over a broader range as vapor generation changes. Pressure also matters because it changes how readily a liquid fuel will vaporize. Higher ambient pressure tends to suppress vapor formation, reducing the amount of fuel vapor in the air and shifting the range, while lower pressure allows more vapor to form, expanding the range. Because both temperature and pressure alter how much fuel vapor is present, they can cause the flammable range to vary considerably.

Other factors listed relate more to how heat is transferred or how energy is released, rather than environmental conditions that change how much fuel vapor is in the air for ignition.