Apple has launched an exchange program for 5W European USB Power Adapters that were sold between October, 2009 and September, 2012. The affected adapter is Model A1300. Apple illustrates exactly how to identify it here. Apple has determined that this model may overhead and become a safety risk.
Those with affected adapters are encouraged to make an appointment at a local Apple Store or authorized retailer. Those who can't get to a store may contact Apple directly. All A1300 adapters manufactured during the identified time period will be replaced free of charge.