Wind Chimes
Wind chimes are dangling clusters of metal wire figures, in geometric shapes that hang from the ceilings around the tunnels under Ortuxl. The are made of inexpensive metals like lead and thin or iron, and festooned with glass beads, and enchanted to cause air circulation and purification. They, and the area for about a square meter around them is often blackened and covered with a soot like layer of carbon.
They will suck air past them in a predetermined direction and replace some noxious gasses with. Turning or moving the Wind Chime does not affect the direction or effect, but dislodging it from the ceiling breaks the magic.
A working windchime doesn't jingle, but it causes a noticeable draft and and close, they give off a sound like soft whispering.
In some places, the wind chimes have fallen down or been removed, and in these places the air is noticeably danker and staler, even dangerous.
People have tried reproducing missing wind chimes, but they don't work an are immediately recognizable because they lack the carbon soot layer.