The transom is that small window above the door. Back in the era of swamp coolers, people would keep them open all summer.
Some old ones eventually had screens installed on the exterior to keep bugs out.
Transoms are both a barrio tradition and safe. What burglar brings a ladder to climb through a narrow opening? There are so many easier targets for thieves.
So my suggestion for downtowners who want a little fresh air is to restore their transoms.