The phenomenon where coins gradually become dirty is called tarnishing. Tarnishing occurs when the metal surface of the coins reacts with elements in the environment, such as oxygen or sulfur, causing discoloration and buildup of grime.
The weather and dirt causes rocks to become dirty and leaves a odor
by dirty water
Off roading
Dirty surroundings can be caused by a person not cleaning their home properly. Other causes are poor drainage systems, illegal dumping, and littering.
yes well if its in a dirty plase
dirty fuel filter
dirty coil
Dirty connection
too many dirty sanchezs
Dirty Air Filters or dirty coil on inside unit.
It can't transfer heat as efficiently when the exchanger is dirty.