If ignited, foam can produce rapid flame spread, intense heat, dense black smoke and toxic gases. Material can melt into a burning liquid that can drip and flow. Accumulated polyurethane dust can be readily ignited and presents a fire risk. High concentrations of dust in the air can explode if exposed to a flame, spark, or other ignition source.
— Unusual fire & explosion hazards of memory foam as provided by Foamorder.com.