Oil filled heaters use heat-conserving oil as the main source of their heat. This oil is fully sealed, is never exposed, and never needs to be replaced. To operate, the radiator oil is heated internally and then circulated throughout the unit's coils and fins; the warm fins heat the air and circulate it into your room. Because the warm air is circulated through simple convection, oil filled heaters operate silently and are very energy efficient. Generally these units have a lower surface temperature than other heater types, so they are very safe to use around small children and pets.