Safety considerations in electrical work

For your purposes here, one rule applies concerning safety around electrical apparatus. If you are in the slightest doubt about whether or not something is safe, leave it to a professional electrician. Household voltage, normally about 117 V but sometimes twice that, or about 234 V, is more than sufficient to kill you if it appears across your chest cavity. Certain devices, such as automotive spark coils, can produce lethal currents even from the low voltage (12 V to 14 V) in a car battery.
Consult the American Red Cross or your electrician concerning what kinds of circuits, procedures and devices are safe, and which kinds aren’t.