I live in a victorian block of flats and we are considering replacing our individual front doors with new fire doors.  However, one resident has asked about the likely fire resistent properties of the existing doors.  Whilst we know that a current door would not give full fire protection, even with suitable replacement letterbox, self-closing mechanism and intumescent seals being added, would it be possible to roughly estimate the possible fire safety properties of our current doors?  Would they give, say, 60% of the protection that a new fire door would provide?  The doors are 44cm thick at most, other than the panels, and are the original victorian ones.  I read that other safety measure can be added to make the existing doors a full fire door, but that this could possibly be more expensive, and difficult, than an entirely new door.  Our block is only three and a half levels above ground, and we now have recently fitted security lighting and a fire alarm system.  Your thoughts would be appreciated.

Check out https://www.asdma.com/knowledge-centre/ and select Risk Assessment Considerations for Timber Fire Doors ASDMA Guidance for Responsible Persons which will provide a lot of useful  information, but you need an expert to inspect the doors and tell you what you need to do, i would suggest you check out http://fdis.co.uk/ . I also assume you are in purpose built flats and you could also study Fire safety in purpose-built blocks of flats.