Are power inverters safe to keep inside my flat / apartment?

You got a misconception about them releasing hydrogen as that is done in small amounts They are totally safe to keep though keep it on a place that you think is far from inflammable stuff and yes you would need to keep something for it as for its base as it releases alkaline and acidic stuff that might ruin your floor

i think the amount of gas emmited is very less...so that wont be such a grave problem as u say...if u wanto ensure safety for ur fear of hydrogen gas being emitted then wat you should do it keep it in a place faar off from the main rooms of ur flat..it would be good if theres a external vent in the place where its kept ..like u c for exhaust fans n all...but ..u neednt worry abt the poiening aspect...inverters r safe...

I've had a battery/inverter set up in the living room for a long time now, has never hurt anything, I mean over a year... I should probably find better storage for it, but I don't wat it misplaced.