Quoted from pinwiztom:My home was built in 1928. Its wiring originally all knob and tube with cloth covered wiring, and no ground.
In the late 70s they did a partial remodel and addition, remodeling the kitchen,
adding on a Master bedroom and finishing the basement.
With the remodel and additions they obviously brought things up to code, though in the other
50% of the house were no work was done
it still has the old wiring and two prong outlets/plugs.
When we bought the house 10 yrs ago, in order to get the house insured,
the insurance company made use change out all the knob and tube wiring
with grounded romex wiring in all the areas with exposed wiring in the garage and attic.
Obviously any wiring within the old walls and old sockets are still knob and tube and non grounded.
In the last few years, I have taken it upon myself to hire an electrician to install one or two
GFCI outlets in all the bedrooms upstairs and the foyer and dining and living & family rooms
which were not grounded, so in doing that it will give each room some grounding effect protection
while providing some outlets with 3 prong plugs, to avoid having to use those cheater plug adapters.
If you ever worry about old wires arcing for some reason, you can get an Arc Fault Interrupter (AFCI).
https://www.leviton.com/en/products/residential/gfciafci/afci
We had a lightning strike nail the house. Direct hit, really interesting following the path it took. I knew the insurance company wasn't interested in checking the wiring in the walls near the strike (nor did I want my walls torn apart), so I got them to pay for AFCI breakers in the panel.