This is the 12542nd most frequent Polish word.
napełniania
"Filling" or "refilling."
In this sentence, "napełniania" is a noun in the genitive case, referring to the action of filling.
Proces napełniania butelek wodą jest automatyczny.
The process of filling bottles with water is automatic.
Here, "napełniania" is a noun in the genitive case, specifying the purpose of the helium.
Do napełniania balonów używamy helu.
We use helium for filling balloons.
In this usage, "napełniania" is a noun in the genitive case, describing the ongoing activity of filling.