While you can tell if a knob and tube wire is active by following the wires and seeing where they lead to, the safest way is to hire a professional. At Langstaff and Sloan, we send one of our licensed electricians to inspect your home’s wiring and see what condition it is in. Alternatively, if you have some technical knowledge of electricity, you may also use a voltage stick, otherwise known as a “tick buster.” By inserting the probes into the knob and tube fixture, you may test the alternating current. If the result is within 110 to 120 volts, the wire is live, so proceed with caution.