Abstract: A method is provided for validating, at a pre-determined test temperature, the operation of a temperature sensor, controller or monitor in a temperature-controlling device having a temperature-controlled environment to be maintained at a target temperature. A standardized temperature sensor is positioned within the temperature-controlled environment. A thermal mass having a temperature different from the target temperature is provided and placed within the environment. The temperature of the environment is caused to deviate from the target temperature in response to the thermal mass. A comparison between the temperature indicated by the sensor, controller or monitor and the temperature indicated by the standardized sensor is made when the temperature of the environment corresponds to the test temperature.