Aluminum wiring was used in some homes from the mid 1960s to the early 1970s. It is a probable fire hazard because of problems regarding expansion, micro-fretting and arcing at connectors, which can cause overheating at connections between the wire, devices or at aluminum wire splices.
Also, the connection becomes warmer when current flows through wires. The expansion of the aluminum, confined under a screw terminal, generates immense pressure that allows the metal to flow into empty spaces in the connector. When the electrical load is removed, the aluminum cools and contracts before a gap forms between the wire and connector. After that, the slightly loose-fitting connection has a much higher resistance, but more corrosion forms in the gap. This corrosion then further increases resistance unfortunately. These connections can become hot enough to start a fire without ever causing the circuit breaker to trip. Aluminum is mostly thought to have a useful life of around 30 years.