Cov qhov rooj hluav taws yog qhov hluav taws kub nrog qee qhov hluav taws kub, xws li cov hluav taws kub hnyiab, kev khiav tawm stairwells, ntsug shafts, thiab lwm yam. Peb muaj daim ntawv pov thawj hluav taws kub qhov rooj, txais tos sab laj nrog peb.