Aluminum is a fine conductor of electric current. It is much cheaper than copper. Just about all the exterior wire on utility poles (all in most areas) is aluminum. If it were copper people would be climbing the poles to steal it and sell it for scrap.
Multi strand aluminum wiring is not at all deemed to be hazardous. Electric flows around the exterior of the wire so having multi strands of aluminum provides the added paths for power so to speak as to allow that type wire to be used without a problem. Good electrical contractors use anti oxidant compound in order to make sure the aluminum does not oxidize. Use care if you ever come across what looks like black goo around wire connections, it is a conductive anti oxidant that is as much of a conductor of current as the wire itself.
The problem with single strand aluminum wiring is the connections oxidize develop high impedance connections and get hot. Connections can get so hot they can allow a house fire to occur. Even connections that do not get hot enough to ignite wood can get hot enough to lower the ignition temperature of wood by a process called pyrolysis.
Copper to aluminum connections must be made a certain way in order to avoid creating an even greater hazard.
One of the problems faced by home owners who wish to make their aluminum wiring safer is a lack of qualified and willing contractors. Most electrical contractors do not wish to take the risk of working on homes with aluminum wiring.
Michael Del Greco is President of Accurate Inspections, Inc., a home inspection business .
He has been a home inspector since 1993 and prior to that spent seven years as a construction project manager.