In the pictures you can see the sand behind the door.
In the first, its just sitting there like a good blob of sand.
In the second, after a dupe has gone through the door, the sand decides it would like to jump about for a bit, it does settle back down, but its weird seeing sand jumping up and down like that.
No real gameplay impact other than messing with my eyes and focus on other more important things.
Build a pnuematic door where some material is on the ground. Don't sweep it away. Then have a dupe use the door.