ᐅ Where is a fire door required?

Hello everyone,
my question is basically covered by the subject, but to be a bit more specific:
Attached you will find the floor plan of the basement of the house we purchased. There is still some time before we move in, but we are already thinking ahead.
The heating system is located in the room labeled "Basement 1." This room is separated from "Basement 2" by a fire-rated door.
In addition, the living area is separated from "Basement 2" (door near the stairs) by another fire-rated door.

In this case, is the latter fire-rated door mandatory, or could it be replaced with a standard door?

Thank you very much for your answers.

Hello

With the heat output I expect from the heating system and the stored fuel quantities, a building permit / planning permission is generally not required.

Olli

The gas heating system, as far as I remember, has a capacity of 27 kW. One thing I forgot to mention earlier: from the basement, you can access the living room via the stairs, where there is a fireplace installed. Could this situation possibly require a fire-rated door?

The background to my question is that we have two cats, and their litter box is planned to be placed in the basement. For energy efficiency reasons, I do not want to remove the door to the basement, but I am considering installing a different door that could include a cat flap.