Are all steel doors fire resistant?

yes and no. anything made of cold rolled steel will resist fire.. the question is what kind of steel door and whether you are asking if it has an authorized fire label or not. residential steel

• clad doors usually can get a 20minute UL fire rating, but it has

to be labeled by the manufacturer ahead of time.. you need a commercial level hollow metal door to get a fire rating up to 3 hours. you can not have polyurethane core. it has to be foam or honeycomb.