Satisfactory performance during the desired lifetime of contacts and connections depends on many parameters, some of them determined by their design (type, materials, forces, etc.) and others by the environment in which they have to function. Concerning the effects of the environment, special attention must be paid to the polluting substances contained -- usually in very small amounts -- in the atmosphere. Silver and some of its alloys are peculiarly susceptible t tarnishing by the minute quantities of hydrogen sulphide that occur in many environments. The tarnish product is dark in colour and consists largely of beta-silver sulphide. Separable electrical connections employing these metals as contact materials may therefore suffer from increased contact resistance and contact noise as a result.

IEC 60068-2-46 Ed. 1.0 - Identical