Wiki

A failed and a failing RIFA capacitor.

Capacitors connected directly to the mains require a special safety rating. This is Class X for those connected across the mains supply, where a failure could present a fire hazard, and Class Y for those connected between the mains and ground, where the failure could result in an electric shock hazard. Such capacitors must always be replaced with ones of the same class. For domestic equipment, sub-class X2 or Y2 are required. You can find out more about Class X and Class Y capacitors in this article.