The U.S. Consumer Products Safety Commission estimates that the likelihood of having a connection reach fire hazard condition in a house wired with "old technology" aluminum wiring (manufactured prior to 1972) is 55 times that of a house wired with copper wire. There is genuine increased fire risk with such a home and the homeowner should make modifications to the house wiring system to lessen the risk. 

It is estimated that there are approximately 2+ million homes across the U.S. that are "aluminum wired." These are homes constructed between the years 1964 and 1974. 

The problem is not with the wire itself, it is intermittent hot connections where the wires join together or connect to devices. The reasons for this can be attributed to the following factors: 

   1. Aluminum wire has a higher coefficient of expansion than copper and expands more when current passes through it. This can contribute to loosening at the connections. 
   2. Aluminum wire must be slightly thicker than copper to carry the same loads and this sizing difference may have contributed to loosening connections in early applications. 
   3. Metals in an oxygen atmosphere oxidize. Copper that oxidizes forms a conductor while aluminum oxide is a resistor. The resistance at the connections causes heat to build. 
   4. Unlike metals which connect can cause an oxide build as well and this may have caused an increased difficulty when aluminum wire was joined to devices intended for copper wire. The oxide added resistance. 
   5. The problem seems to increase as time goes by. This would seem to be due to increased loosening and oxide build. 

Danger Signals: Here are some symptoms that you may have aluminum wiring in your house or that your aluminum wiring may have connection problems. 

1. Flickering lights. 
2. Unusual static on radio or TV. 
3. Reduced TV picture size. 
4.Arcing or sparks coming from switches or receptacles. 
5.Cover plates on switches or plugs hot/warm to the touch. 
6. Plugs and lights that don't work. Dead circuits. 
7.Circuit breakers that trip for no apparent reason. 
8. Arcing sounds within main distribution panels. 
9.Melted insulation on conductors near connections. 
10. Burning plastic odors near plugs or switches or lighting. 
11. Smoke from switches or plugs or junction boxes. 
12.Light bulbs that burn out quickly or shine unusually bright. 

Making Aluminum Wiring Safer: A variety of modifications have been practiced over the years but only the "COPALUM" method is considered acceptable by the U.S. Consumer Products Safety Commission. 

US CPSC Pub#516 Repairing Aluminum Wiring

Warning: Working with older aluminum wire is more difficult than working with copper wire. An inexperienced electrician can do more harm than good. Aluminum wiring safety retrofits are best left to specialists.