Pollution degree is a classification according to the amount of dry pollution and condensation present in the environment. This classification is important since it affects creepage and clearance distances required to insure the safety of a product. Office and laboratory areas are considered pollution degree 2 environments according to safety standards and certification bodies. Pollution degree 1 may be considered inside sealed components and within air/water tight enclosures. Pollution degree 3 is a harsher environment typical in many industrial manufacturing areas. Safety standards bodies such as Underwriters Laboratories (UL) and IEC  categorize them as follows:
Pollution Degree 1: No pollution or only dry, nonconductive pollution occurs. The pollution has no effect.
Pollution Degree 2: Normally only nonconductive pollution occurs. Temporary conductivity caused by condensation is to be expected.
Pollution Degree 3: Conductive pollution or dry nonconductive pollution that becomes conductive due to condensation occurs. To be found in industrial environment or construction sites (harsh environments).
Pollution Degree 4: The pollution generates persistent conductivity caused by conductive dust, rain, or snow.
See table 1 for examples of each of these environments [2,3].
Table 1. Examples of pollution degree environments
Clearly, ATE environments (i.e. Test Stations) are categorized as “Pollution Degree 2”. Any equipment designed for, or placed in a test station environment should have a pollution degree 2 rating in order to meet recognized safety standards.