|This article is about an older version of DF.|
The tracking of contaminants is a configurable option, which defaults to NO in Dwarf Fortress mode and YES in adventure mode. The actual options are WALKING_SPREADS_SPATTER_DWF and WALKING_SPREADS_SPATTER_ADV in d_init.txt.
Water that flows over contaminants can pick them up, multiply them, and redistribute them as the water moves. Water does not appear to move mud, although mud will be created any time water covers a tile. The mechanics of redistributing contaminants using water is not well understood although there have been some observations of strange behavior when mixing blood and water.
- adding 7/7 water on top of a pool of blood creates more pools of blood at the edge of the water as it moves and evaporates.
- an overflowing reservoir that contains some blood creates blood everywhere the water flows.
- water will create mud on any non-muddy tile, and moving water will frequently redistribute the mud.
Removing contaminants can be accomplished by dwarves performing a cleaning. This requires a contaminant to be on a floor tile, and will (as a side effect) also remove contaminants from adjacent walls. A contaminant that is on a wall, with no adjacent contaminated floor, will never be cleaned. Contaminants are also removed if any real building is built on them (dirt roads are not buildings), even if that building is subsequently removed.
Note that atom smashing a square with a contaminant on it will not remove the contaminant.
Contaminants can be moved from creatures to floor tiles with water. The simplest and most effective way is to have the creature walk through a 2/7 or 3/7 water tile. All contaminants will be transferred from the creature to the floor, and it will walk away wet (water coverings in inventory) but otherwise uncontaminated. Another way is to drop water on a creature as it's walking over a floor grate (e.g. a waterfall). This is much more complex to set up, and has an additional drawback: a dwarf who attempts to clean the contaminated floor grate tile will be interrupted by the sudden influx of water, resulting in job cancellation spam, and an uncleaned grate (unless you temporarily turn off the waterfall).