It is produced by many buildings involved in processing items and spreads outwards at a steady rate.
The evolution factor is not increased by the spreading/absorbed pollution, but by the pollution produced by all the Player's machinery at every tick. The pollution cloud is used to trigger biter attacks and determines the size of the attacks.
- Main article: Achievements
Pollution is directly connected to the following achievement:
- It stinks and they don't like it
- Trigger an alien attack by pollution.
As soon as a chunk has reached 15.0 pollution it starts spreading in all four cardinal directions at a rate of 2% game second (60 ticks).
e.g. a chunk with 400.0 pollution and 4 adjacent chunks with 100.0 pollution each, raises the pollution in all adjacent chunks by 8.0 while reducing its own pollution by 32.0. But everyone of the 4 surrounding spreads 2.0 pollution "back" to the center chunk, so it only loses 24.0 + absorbed value.
- Every Chunk (32x32) of map slowly reduces the pollution it covers (See Pollution Production#Chunks). So the more the pollution spreads, the more is absorbed.
- Trees also absorb some pollution (See Pollution Production#Trees).
- Spawners absorb a great amount of pollution.
- In certain Mods it is possible to build devices or trees which reduce pollution.
Each spawner absorbs 20 + 0.01 * [chunks pollution] every game second (60 ticks), if the chunks pollution is greater than 20 otherwise it absorbs the total pollution.
Higher pollution values decrease the time it takes for biters to join the attack force. After a certain amount of pollution is absorbed the spawner sends one of its biters/spitters to a rendezvous point. Every 1 to 10 minutes (random) the mustered biters launch an attack. If not all biters have arrived at the rendezvous point by that time, they will wait up to an additional 2 minutes for stragglers.
Required pollution to add an additional biter/spitter to the attack wave:
With 1350 absorbed pollution at the time of attack the following wave consists of 6 small biters and 1 medium biter OR 6 small spitters and 2 medium spitters depending on the spawner's type and evolution factor.
Modules that list "+x% pollution" increase pollution multiplier, not a flat pollution rate. Final pollution value is (pollution multiplier * energy usage multiplier * base pollution), meaning heavily boosted buildings are likely to account for most of the pollution produced in a factory.
These tables contain information about the levels of pollution produced/absorbed by items in the game.
|Object||Pollution per KW per game second (60 ticks)||Pollution per game second at full power|
If a chunk's pollution is greater than 20, each enemy spawner absorbs 20 + 0.01 * [chunk's pollution] every game second (60 ticks), otherwise it absorbs the chunk's total pollution.
Every chunk has a natural absorbtion rate per tick which is determined by the weighted average of its floor tiles.
Following numbers are the pollution reduction for a full chunk (32x32 tiles) composed of the same floor tiles per tick.
|Tile||Pollution per tick||Pollution per second|
|medium dry grass||-0.0075||-0.45|
|Deep green water||-0.0083||-0.5|
Pollution per tick resembles the third number in the pollution debug information (which is missing the 5th digit)
Every single tree absorbs a small amount of pollution in its chunk per tick.
|Object||Pollution per tick||Pollution per second|