Unless really describing a result of a chemical reaction in the context of chemistry, I wouldn't choose to use the word residue, and the sterilization of products is not IMHO chemistry. And in a non-chemical context, a residue would usually be understood to apply to some solid matter, and not to a gas.
Residual is usually an adjective, and although it also has some uses as a noun, none of them are applicable here.
I would translate your sentence as "After sterilizing products with ethylene oxide, some of this gas can remain in the packaging." or possibly "After sterilizing products with ethylene oxide, some residual gas can remain in the packaging."