What characteristic of a liquid generally makes it classified as flammable?

A liquid is generally classified as flammable based on its flash point, which is the lowest temperature at which the liquid produces enough vapor to form an ignitable mixture with air. A low flash point indicates that the liquid can easily produce flammable vapors at room temperature, making it more likely to ignite.

This characteristic is critical in determining how hazardous a liquid is when it comes into contact with ignition sources. The lower the flash point, the more hazardous the material is in terms of fire risk. In contrast, liquids with a high viscosity or a solid state at room temperature do not readily release vapors conducive to combustion, while a strong odor is not necessarily indicative of a liquid’s flammability but is more related to its chemical properties or potential irritants. Therefore, the defining feature that classifies a liquid as flammable is its low flash point.