At what temperatures is Avgas most susceptible to ignition?

• A. 100 to 165F
• B. 0 to 50F
• C. -100 to -20F
• D. -50 to 30F

Answer: (D)

The key idea is how vapor formation and flammability depend on temperature. Avgas has a very low flash point, about -50°F (-45°C). At temperatures near this point, enough fuel vapor is produced to mix with air in the flammable range, so a small ignition source can trigger a flame. As temperatures rise toward about 30°F, there’s still plenty of vapor to form an ignitable mixture, so ignition remains highly possible. Outside this window—much colder—the vapor production drops below what’s needed for ignition, and much warmer, the mixture can move out of the flammable range or the vapor may dissipate differently—reducing ignition risk. For these reasons, the temperatures around -50 to 30°F are where Avgas is most susceptible to ignition.