What is the switch actually doing? It looks like all it is doing is converting fiber to copper and you’d be better off with a media converter that should require no vents. Is the UPS required? If you went to a media converter you might be able to use a UPS that is much smaller and no cooling fan. Then you would have no air flow and no/low dust issue.
May not work for other areas, but something to consider. There are also some fanless small switches like some of the Mikrotek stuff that might do what you need.
I’d say to use a smaller rack, but I know there aren’t many choices for wall mount stuff. With a smaller rack you might be able to seal and filter it better.