Qhov zoo ntawm cov qhov rooj steel hlau yog hluav taws kub thiab rwb thaiv tsev kub. Vim tias cov ntaub ntawv ntawm lub qhov rooj hluav taws kub yog cov khoom siv hlau, lawv cov hluav taws kub zoo heev. Raws li cov hluav taws kub sib txawv, steel qhov rooj hluav taws tuaj yeem muab faib ua peb qib: A, B thiab C. Steel fireproof qhov rooj ntawm cov qib sib txawv tuaj yeem siv rau ntau qhov chaw.