Confirm the location
Record the room, building layer and what sits above, behind or beside it.
↝Odors
Visual Match pattern
Odor when extract fan runs
Pressure imbalance can draw air from drains, cavities or lower spaces.
Visual resemblance is only the first clue.Location, timing, texture and what makes it change are more useful than color alone.
Decode this pattern →Watch the trigger
Rain, water use, temperature and equipment cycles separate causes.
Verify before repair
Use the next distinguishing check instead of treating the surface appearance.
