What term describes the temperature at which vapors from a material form an ignitable mixture?

What term describes the temperature at which vapors from a material form an ignitable mixture?

• A. Autoignition temperature
• B. Boiling point
• C. Flammability limit
• D. Flash point

Answer: (D)

The concept being tested is the flash point—the lowest temperature at which a liquid’s vapors can form an ignitable mixture with air in the presence of an ignition source. At this temperature, there is enough vapor in the air to ignite if a flame or spark is present. Below it, there aren’t enough vapors to sustain ignition; above it, ignition becomes possible. This differs from the autoignition temperature, which is the temperature at which the material will ignite without any external flame or spark. Boiling point is about when a liquid turns to vapor, not when those vapors can ignite. Flammability limit refers to the range of vapor-to-air concentrations that will burn, not to a specific ignition temperature.

The concept being tested is the flash point—the lowest temperature at which a liquid’s vapors can form an ignitable mixture with air in the presence of an ignition source. At this temperature, there is enough vapor in the air to ignite if a flame or spark is present. Below it, there aren’t enough vapors to sustain ignition; above it, ignition becomes possible.

This differs from the autoignition temperature, which is the temperature at which the material will ignite without any external flame or spark. Boiling point is about when a liquid turns to vapor, not when those vapors can ignite. Flammability limit refers to the range of vapor-to-air concentrations that will burn, not to a specific ignition temperature.