One is a heavy-duty AC-powered air pump that would probably run for hours non-stop if I needed it to. It is similar to this Porter-Cable unit, available on Amaznot:
https://www.amazon.com/PORTER-CABLE-..._id=9022396011
This one stays in the garage. The van has a slightly less robust 12-volt air pump; our two other vehicles have cheap Walmart sourced tire inflators. In the van I also have a spray can of tire fixing goo and a packet of tire patching plugs, all of which I greatly wish never to use.
Before every trip, I check the van's tire pressure with a gauge and top off if necessary with the Porter-Cable air pump. I try out the others every once in a while to make sure they still work.