2, used to determine the electrical clearance or creepage distance of the micro-environmental pollution level can be divided into 4 levels. Pollution level 1 is no pollution or only dry non-conductive pollution. Pollution level 2 is the general situation only non-conductive pollution, but must take into account the occasional condensation due to transient conductivity. Pollution class 4 is caused by persistent conductive pollution, for example due to conductive dust or rain or snow.
3, unless otherwise specified in the relevant product standards, industrial appliances are generally selected for pollution level 3 environment, household and similar appliances are generally selected for pollution level 2 environment.