This is the 12542nd most frequent Polish word.
napełniania
"Filling" or "refilling."
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 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.
In this usage, "napełniania" is a noun in the genitive case, describing the ongoing activity of filling.