IAAI Certified Fire Investigator (CFI) Practice Test

The concept here is ignitable liquids—the liquids that can fuel or accelerate a fire and may seep into porous materials like concrete. When such residues are trapped in a concrete floor, investigators can recover them by using absorbent powders such as lime, diatomaceous earth, or non-self-rising flour. These powders pull the hydrocarbon residues out of the concrete pores so the sample can be collected and analyzed in the lab. This approach works because ignitable liquids readily leave behind trace amounts in porous substrates, even when the liquid isn’t visible on the surface. Gasoline is an example of an ignitable liquid, but the question refers to the general type of material, not a specific substance. Vapors describes the gaseous phase and isn’t the material trapped in the concrete; accelerants is a broader term for substances that speed combustion, not the category of material being recovered.