PIR is at times stated to be fire retardant, or contain fire retardants, however these describe the results of "small scale tests" and "do not reflect [all] hazards under real fire conditions"; the extent of hazards from fire include not just resistance to fire but the scope for toxic byproducts from different fire scenarios. A 2011 study of fire toxicity of insulating materials at the University of Central Lancashire's Centre for Fire and Hazard Science studied PIR and other commonly used materials under more realistic and wide-ranging conditions representative of a wider range of fire hazard, observing that most fire deaths resulted from toxic product inhalation. The study evaluated the degree to which toxic products were released, looking at toxicity, time-release profiles, and lethality of doses released, in a range of flaming, non-flaming, and poorly ventilated fires, and concluded that PIR generally released a considerably higher level of toxic products than the other insulating materials studied (PIR > PUR > EPS > PHF; glass and stone wools also studied). In particular, hydrogen cyanide is recognised as a significant contributor to the fire toxicity of PIR (and PUR) foams.