What causes “pattern staining” on a ceiling tile?
Pattern staining on the face of a ceiling tile may be due to three adverse causes. 1) Dirty water may have dripped onto the back of the tile and soaked through to the face causing discoloured stains. These will normally be yellow or brown in colour and probably due to ferric oxide (rust) contamination. 2) Tiles in the immediate vicinity of air grilles or diffusers sometimes display black marks or streaks. This is due to dirt in the air being deposited on the tile’s surface as the air emanates from or returns to the distribution system. Smooth tiles such as Plain or Orcal plain etc are less likely to be affected. 3) Heat from a room will rise (due to convection) and migrate through a suspended ceiling towards the (normally) cooler ceiling void. Minute particles of dirt in the atmosphere will also rise and be deposited on the ceiling tile’s surface. However if the thermal insulation of the tile is not consistent (as often occurs with metal tiles with mineral wool pads in the back, that a
