Accelerants are substances that significantly alter a fire’s behavior, causing it to develop and spread more rapidly than it would naturally. These materials dramatically increase a fire’s intensity and destructive potential.
Understanding Accelerants: Definition and Key Properties
An accelerant is defined as any substance or mixture that speeds up the combustion process of a fire. These materials are often liquids, but can also be gases or solids.
Accelerants possess high volatility, meaning they evaporate readily at ambient temperatures, forming flammable vapors. They also exhibit a low flash point, the lowest temperature at which their vapors can ignite in the presence of an ignition source. These properties allow them to quickly generate a significant amount of fuel in the form of vapor, crucial for rapid fire development.
Common Categories of Accelerants
Accelerants encompass a range of readily available substances, often categorized by their chemical composition. Petroleum distillates represent a major group, including common examples such as gasoline, kerosene, and lighter fluid. These are mixtures of hydrocarbons, varying in their volatility.
Another category includes alcohols, like ethanol and isopropyl alcohol, often found in household products or solvents. Various other flammable solvents, such as paint thinners and acetone, also serve as accelerants. These substances are frequently used due to their widespread accessibility.
How Accelerants Intensify Fires
Accelerants intensify fires primarily by making ignition easier and accelerating the rate at which combustion occurs. Their low flash points allow them to ignite with minimal energy input, often from a small spark or flame. Once ignited, accelerants vaporize rapidly, releasing a large volume of flammable gases.
This rapid vaporization provides an abundant fuel source, leading to a swift increase in flame size and heat output. The fire spreads quickly across surfaces coated with accelerants, significantly increasing the “heat release rate” of the fire. This rapid escalation can make fires much more difficult to control and lead to dangerous conditions.
Identifying Accelerants in Fire Investigations
Identifying accelerants in fire investigations involves a combination of field observations and laboratory analysis. At a fire scene, investigators look for unusual burn patterns, such as irregular shapes or areas of unusually intense damage, which can suggest the presence of an ignitable liquid. Porous materials like wood or carpet, and cracks in flooring, are often sampled as they can trap accelerant residues.
Specialized tools like hydrocarbon sniffers or accelerant detection canines are used to pinpoint areas with ignitable liquid residues. Collected samples are then sealed in airtight containers to prevent evaporation and sent to forensic laboratories. The most common and reliable laboratory technique for identifying accelerants is Gas Chromatography-Mass Spectrometry (GC-MS). This instrument separates the complex chemical mixture of the residue and identifies individual compounds, comparing their patterns to known accelerants to determine their origin.