Safety capacitors play a role in reducing the chances of a fire or electric shock for electronics connected directly to mains electricity. Mains electricity is also known as AC power, line power, utility power, or household electricity. Wall sockets or electrical outlets have constant power provided to them at a nominal voltage and frequency, but this power contains electromagnetic interference (EMI). EMI needs to be filtered for many electronics to work properly. Safety capacitors are used in these EMI filters because they are rated to handle transients and surges typical to mains electricity, which means they must have a robust design and undergo extra testing to ensure a high level of reliability.