"Free float of RMS was 192.25m on 01/12" from your post can't be correct (assuming its this year). Mistake on the part of FT i'd guess, unless I've missed an RNS of an unknown holder selling best part of a billion shares this week.
If you check this website archive, https://web.archive.org/web/20200815000000*/Volzfilters.com The last snapshot of voltzfilters.com with a working website was jul 2019. Checking the snapshots of this year shows what you see today
Not just building air con systems either. Aircraft, cruise ships. Lots of possibilities, plus wouldn't take much to retrofit this material into existing filter designs.
You've linked to the wrong Volz company. The one we're dealing with is Volz Filters https://volzfilters.com/ , not Volz Gruppe that your original post shows.