Safety switches are designed to save lives. They detect the loss of current from a circuit that indicates a person is receiving an electric shock, and they cut the power in as little as 30 milliseconds. Safety switches have been mandatory on the power outlet circuits of new homes since the early 1990s, and on the light and power circuits of new homes in most states since 2000. But many older homes do not have safety switches, and circuits such as air-conditioning, pool filters, hot water and stoves are not protected in most homes.