Right. As far as out-gassing, I'd be more concerned with the liner material itself. I use it
under the tile floor (taped seams & edges) to catch anything that may--pun intended--slip through the cracks. Keeps any out-gassing to a minimum, because there's no exposed vinyl.
Even though ZaRDoZ is paper trained, he isn't 100%, and does occasionally dump a big wet stinkie right on a seam between tiles. Fortunately, the
Nature's Miracle for Stinky Dragons I use is very good at seeping down those same cracks, killing any odors, bacteria, etc. When opening the enclosure doors, all anyone can smell is basil (from the basil forest). IME, vinegar takes a while to dissipate--may be less of an issue with a screened/open top.
If you're using it as a liner under paper towel, I'd just tape it down on the edges & seams so it can be replaced if necessary. Covering it with paper towel should also reduce outgassing.
I really don't know how much of an issue the outgassing is (but I tend to err on the side of caution). I
do know that it's come up in questions about the product(s) on Amazon.
non-adhesive shelf liner "outgassing"
https://www.amazon.com/product-reviews/B01J7X4XKI?reviewerType=all_reviews
https://www.amazon.com/ask/questions/TxTXMTFS7W5N3P/ref=ask_ql_ql_al_hza