Where are self-closing doors required on a MODU?

Correct Answer: Option D — In each stair tower

Under 46 CFR 108.160, self-closing fire doors are required in each stair tower on a Mobile Offshore Drilling Unit (MODU). Stair towers serve as critical vertical escape routes, and self-closing doors prevent the rapid spread of smoke, toxic gases, and fire between deck levels during an emergency, maintaining structural fire integrity.