I live in a home built in 1931. Most of the wiring is original knob and tube, except for the kitchen and bathroom which were upgraded in the 80's and have more modern plastic-clad wiring.
The kitchen and bathroom outlets are all 3 prong, but only one or two outlets are grounded, the others aren't (the ground wire is either missing entirely or it's there but seems to not be connected). The bedrooms outlets are all 2 prong.
I would like to replace all the outlets in the kitchen and bathroom with GFCI outlets, even if the missing ground makes them somewhat less useful.
I also seem to recall reading somewhere that having GFCI in the bedrooms is a good idea, to help with sparking or something.
Any thoughts on this? Is this in keeping with current electrical codes, even if the ground seems to be missing or non-functional throughout most of the kitchen/bathroom?
I'd suggest an inspection by a qualified electrician to check the integrity of the knob and tube.Also were the connections of the upgrades made to the panel or the knob and tube.For the bedrooms you are thinking of arc fault breakers.
Aside from running new wires, installing GFCI outlets is the right thing to do if you need 3-prong outlets. They still provide some extra protection even without a ground. They need to be labeled "No Equipment Ground"; most GFCIs should come with a sticker for this.
As far as bedrooms and sparking, yes, you're thinking of AFCIs. Replacing the circuit breakers for the knob & tube circuits with AFCIs can be a good idea, and is sometimes recommended. Theoretically, the AFCI will trip if there is a bad splice or broken wire arcing somewhere. They can provide additional protection for old wiring.
That said, having the existing knob and tube checked out by an electrician can't hurt. Old houses can have a lot of creative wiring done over the years, and it's not always done in the safest ways...