▁tr ic ar b ony l . ▁ ▁Fe ( CO ) 5 ▁is ▁used ▁in ▁the ▁production ▁of ▁" car b ony l ▁iron ", ▁a ▁fin ely ▁divided ▁form ▁of ▁Fe , ▁a ▁material ▁used ▁in ▁magnetic ▁cores ▁of ▁high - fre quency ▁co ils ▁for ▁rad ios ▁and ▁televis ions ▁and ▁for ▁manufact ure ▁of ▁the ▁active ▁ing red ients ▁of ▁some ▁rad ar ▁abs orb ent ▁materials ▁( e . g . ▁iron ▁ball ▁paint ). ▁It ▁is ▁famous ▁as ▁a ▁chemical ▁prec ursor ▁for ▁the ▁synth esis ▁of ▁various ▁iron - based ▁nan op articles . ▁ ▁Iron ▁pent ac ar b ony l ▁has ▁been ▁found ▁to ▁be ▁a ▁strong ▁fl ame ▁speed ▁in hib itor ▁in ▁o xygen ▁based ▁fl ames . ▁A ▁few ▁hundred ▁p pm ▁of ▁iron ▁pent ac ar b ony l ▁are ▁known ▁to ▁reduce ▁the ▁fl ame ▁speed ▁of ▁sto ichi ometric ▁m eth ane – air ▁fl ame ▁by ▁almost ▁ 5 0 %. ▁However ▁due ▁to ▁its ▁to xic ▁nature ▁it ▁has ▁not ▁been ▁used ▁widely ▁as ▁a ▁fl ame ▁ret ard ant . ▁ ▁To x icity ▁and ▁ha z ards ▁Fe ( CO ) 5 ▁is ▁to xic , ▁which ▁is ▁of ▁concern ▁because ▁of ▁its ▁vol at ility ▁( v ap our ▁pressure : ▁ ▁at ▁ 2 0   ° C ). ▁ ▁If ▁in h aled , ▁iron ▁pent ac ar b ony l ▁may ▁cause ▁lung ▁ir rit ation , ▁to xic ▁p