Large and small slow cookers are safe to use unattended, according to the Crock-Pot brand. However, some slow cooker models have been recalled due to fire hazards.
Some models of the Bella Kitchen slow cooker were recalled in 2010 when the company learned that some control panels had melted and sparked. The Crock-Pot company recommends using safety precautions when leaving the house, including filling the cooker between half and three-quarters full and making sure the device sits on a flat, hard surface. The cooker's power cord also should be arranged so that it doesn't come in contact with the hot unit.