The primary parameter for evaluating the flammability hazard posed by the liquids is the ________.

• A. Flash point
• B. Autoignition temperature
• C. Boiling point
• D. Viscosity

Answer: (A)

The key factor in assessing how flammable a liquid is lies in how easily its vapors can form an ignitable mixture with air. The flash point is the lowest temperature at which enough vapor is released to mix with air and ignite in the presence of an ignition source. This makes it the most practical and direct measure of flammability risk for everyday handling and storage: a liquid with a low flash point can ignite with relatively little heat.

Autoignition temperature, while related, refers to the temperature at which the vapor-air mixture ignites without any flame or spark, and it is typically much higher and less relevant for routine safety decisions. Boiling point indicates when a liquid turns to vapor, not whether the vapor can ignite at common handling temperatures. Viscosity affects how a liquid flows and evaporates, but it doesn't directly determine ignition risk.