Arclight

I look after some holiday lets, and with the new regulations coming out affecting holiday homes, they say that all doors on the escape route should be "notional fire doors". My understanding is that this means the doors should be of a standard that was thought to be fire doors at the time of construction, but several of these houses are over 100 years old, and still have the original doors. At that time fire doors weren't really a thing, so how does that apply? I also have a couple of newer houses that have solid doors, but no intumescent strips, which at the time were fitted to meet the building regs requirement for FD20 doors. Do these now need fire and smoke seals fitting?