Fire rated door requirements

[Brian Moran]

I have a single story four Plex in Lucas County, Ohio, built in 1973. There’s a common hallway down the middle with a door on each end that exits to the outside. There are two units on each side of the hallway.

I am planning to replace all the doors because they are old, damaged and outdated in appearance. The store pricing the doors asked me what fire rating I need, telling me that it’s required.

My hour long, google search has, dry, there are some similar post from about 10 years ago in BiggerPockets, but don’t answer my question.

Are fire rated doors required for the two exits, and apartment entrances? Of so, has anyone found the code reference that explains the requirement; 20-minute, 90-minute, etc. 
I plan on making a lot of phone calls tomorrow, but wanted to check in here. I will post what I find.