If it smells like fish in your home & you can't find the source of this smell.
(I've found this on Facebook and I haven't known this before so I'm going to share it with you)
Probably you first look for some leftover fish in the kitchen. If that's not the source you probably clean the kitchen or perhaps the whole flat / house.
But if even that doesen't help or even weirder if the smell disappears but then returns:
it might be a far more dangerous reason:
melting outlets which coult result in your home burning
!
by the way: if you smell eggs it could be foul eggs in the kitchen but it could also be a gas leak!