Somewhere in the net of tubes of our AC we have a machine that produces rocks. They randomly shoot of the air vents, please install ballistic shields in front of the vents to stop them from hitting our customers.
Which sounds insane until you realise that you’ve just described in outline something very like the iron dome missile defence system, which actually exists in reality.
(And of course you’ll get no argument from me that it’s insane that such things need to exist at all, but such is the world we live in.)