I found this configuration odd and I’m not sure what to make of it. This home has a gas furnace and water heater located in a utility closet accessible from the garage. In this closet there are meta-caulk type ring seals around the plastic flue and vent pipes for the high-efficiency furnace. There was a metal fire stop around the water heater flue pipe.
The bad part, I think, is the upper and lower combustion air vents leading to the attic. As this closet is not protected by a fire rated door having the open C-Air vents defeats the purpose of the other fire separation means.
Is there a code reference for this? What do you all have to say? I’m just mulling over how I’m going to write this up - I’m considering just requiring a fire rated self closing door for this room.