At Armstrong Forensic Laboratory, we routinely analyze debris recovered from laundry dryer fires. The clothes dryers we have in our homes heat our clothing to temperatures approaching the ignition temperature of cotton. When there are traces of other contaminants on the clothes, such as residual cooking oils that have a tendency to self-heat, spontaneous combustion fires can occur.
It is important to note that typically, spontaneous combustion fires will not occur while the dryer is running. The tumbling action of the dryer and the forced airflow out the dryer vent prevent the buildup of heat in the clothing. The circumstances surrounding spontaneous combustion clothing fires normally involve interruption of the drying process, before the dryer has completed the “cool down” portion of the drying cycle.
When hot clothes or towels are left in a dryer or piled on a bed, traces of residual vegetable oils, such as cooking oils, can continue to generate heat. Accumulation of the excess heat, under certain conditions, will lead to ignition of the fabric, causing a fire. Typically, if a fire will occur, ignition will occur within less than eight hours after the hot clothes are allowed to stand.
Armstrong Forensic Laboratory has decades of expertise in the analysis of debris from clothing and dryer fires. These samples are commonly analyzed for traces of ignitable liquids, as well as for residual polyunsaturated fatty acids associated with cooking oils, wood stains (drying oils), and other plant-derived oils by a process known as FAME (Fatty Acid Methyl Esterification).
Remember the moral of the story: Don’t interrupt or stop your clothes dryer and always let it complete the cool-down process. Following this rule may just prevent dryer fires from occurring in your home or business.