According to Seacliff Inspections, aluminum wiring was used throughout North America between the mid 60’s until the late 70’s due to the high cost of copper at the time. (Seems like we are back in that situation).
A home built during this time has a good chance of containing aluminum wiring. But, is it safe? The short answer is yes. It is still used in many other applications but not in residential.
Home buyers and owners are finding that many insurance companies are nervous about properties that have aluminum wiring unless they have been inspected by the Electrical Safety Authority of Ontario (ESA). Often an inspection certificate will be required to be sure everything is OK.
Any problems that might occur usually are at the junction boxes and there is seldom a need to rewire the house as the wire running through the walls is normally in good shape. Most problems are where aluminum wire is connected to a copper connection on a junction box or light switch. Because of the difference in the way aluminum and copper deals with electricity, they expand at different rates and the connection could become loose thereby resulting in an arc if a space develops. Connectors are now available to take care of this situation quite easily.
You will suspect a problem if you have aluminum wiring and you have flickering lights but the bulbs are good; switch plates and receptacle covers are warped, discoloured or warm; plugs that don’t work even when there is power to them; smoke or sparking around switches or receptacles or circuit breakers or fuses that trip for no apparent reason.
There have been no cases of a house being burned up that I am aware of, so just keep an eye for the symptoms or call an electrician to check things out.