Degree of Contamination

What is the Degree of Contamination?

The degree of contamination is the value of the expected outside contamination of an electric component. It is mainly determined by the mounting position of the component. The protection class of the component is determined by the degree of contamination of the mounting position. The standard for different degrees of contamination is DIN EN 61010-1. It defines the degree of contamination as "a parameter to measure air and creepage distance of electric components".

As long as an electric component is not incorporated into a resin block, a certain degree of contamination should always be expected. Even a perfectly sealed case may sooner or later allow dirt particles to enter. The components have to be set up to function properly, even when contaminated. Especially for printed circuits this is a big issuer: conducting paths and solder pads are basically open next to each other on a circuit board. Abrasive metal shavings that intrude could cause a short, which would make the entire assembly useless. In general it's not just the component itself that is damaged irreparably. The component presents a fire hazard too. To help engineers designing the assembly the "degrees of contamination" were developed.

What is "Creepage Distance"?

Creepage distance is an unwanted connection in between two conductors created by ionized air (clearance) or contamination. Creepage distances are conductor paths for parasitic currents which may interfere with the functionality of electric assemblies. These interferences can be anything from a light malfunction up to complete destruction. Creepage distance is any potential connection between two open power contacts. Forming of creepage distance is favoured by contamination. A typical creepage distance can be found in an unprotected socket close to a stove. Especially grease residues may condense over time and create creepage distance in between contacts. This can even happen under the plug of a plugged in device. Therefore it is highly recommended to only use sockets with a flap and seals and to regularly check and clean them.

Degree of Contamination 1

Degree of contamination 1 is the lowest allowed contamination. In turn it defines devices in which devices are especially sensitive to contamination and therefore have to be protected.

Degree of Contamination 2

Degree of contamination 2 defines areas that permit low non-conductive contamination. DIN EN 6101-1 defines the degree of contamination in detail as occasional condensation or hand sweat.

Degree of Contamination 3

Degree of contamination 3 is described as conductive contamination (e.g. metal shavings) or contamination that becomes conductive due to condensation. Components installed in such areas have to be appropriately shielded.

Degree of Contamination 4

Degree of contamination 4 is a permanently conductive contamination or through humidity favoured permanent contamination. It is the highest degree of contamination. Components in this area have to be designed sufficiently resistant.

Examples for Degree of Contamination 1-4

An example for degree of contamination 1 is the inside of electric assemblies that are installed in buildings. Regardless of whether they are screwed into plastic cases or if control cabinets with a lock are used, open contacts and conductor paths can be found in each case. Each contamination that exceeds dry non-conductive dust in low amounts quickly causes substantial damage.

Since hand sweat is specifically defined as the maximum amount of contamination in degree of contamination 2, all handheld electric devices are automatically included. These include kitchen appliances such as a hand mixer or an iron as well as power tools. Further examples include all components that have to be touched occasionally: lamps, power supply units, all types of plugs.

Degree of contamination 3 includes devices that are set up close to sources of conductive dust. This includes all processing machines in the industrial sector: metal cutting machines, grinders and their control units have to be shielded sufficiently in accordance with degree of contamination 3.