What is an accelerant?

An accelerant is specifically defined as a substance that is used to enhance the spread of fire. These substances can significantly increase the rate at which fire propagates, making them critical in the investigation of arson cases. Accelerants often include flammable liquids such as gasoline, lighter fluid, and paint thinner, which are used to intentionally accelerate the combustion process. Understanding accelerants is crucial for fire investigators, as their presence can indicate foul play and provide insights into the circumstances surrounding a fire.

The other options refer to different fire-related concepts. Fire-resistant materials are designed to withstand heat and prevent the spread of fire, while a device used to start a fire does not relate to the enhancement of fire spread. The visual indicator of fire intensity does not pertain to substances but rather to methods of assessing how fierce a fire is burning. Thus, the definition of an accelerant is accurately captured in the identification of it as a substance that enhances fire spread.