Fire reg requirements for bathroom extractor fans?

Hi,
I am planning a loft extension, but am not clear what has to happen to the existing extrator fans in my bathroom and ensuite.

They both come out through the ceiling and then vent via PVC ducting into the eves.

After the conversion these would still be there, but behind the wall. Do I have to do anything or use any special material with these at all? I can't seem to work out what is required looking the the building regs, and I want to do this in stead of the builder. Thanks

Brett

The extractor fans when they exit through your ceiling enter a void between your bathroom ceiling and your loft rooms do they not? Therefore they will be within the 1/2 hour protective zone between the two spaces. Technically Building Control could insist they were in their own fire proof ducts but they won't at least I've never known it happen. Bathrooms are low risk rooms.

You said they'll still be there, but behind the wall? Then that's fine.