So i was making an enclosed room in space, the entire area had backwall with a row of airflow tiles. As i understood, the airflow and mesh tiles were not meant to leak so i did a quick test and that was correct. However, i tested it with a mesh tile and an airflow tile and when the test was a success i replaced the mesh tile with an airflow tile.
Fast forward 30 minutes when im trying to fill the room up and it seems to be leaking from where the mesh tile was located. This was the only airflow tile leaking. I was only able to find the leak by using the oxygen overlay and mousing over the airflow tiles.
Place mesh tile in space, replace with airflow tile (do not deconstruct first)