A method of thermal inspection of a turbine component defining at least one internal cooling passageway (110, 120), the turbine component being at a thermal equilibrium state with its surrounding environment, the method comprising: receiving a continuous sequence of thermal images of at least an exit hole defined by the at least one internal cooling passageway (110, 120) at a surface of the turbine component; delivering a pressurized airflow pulse at a stable temperature into the at least one internal cooling passageway (110, 120) of the turbine component, the turbine component at the thermal equilibrium state with its surrounding environment; receiving a temperature response signal (1000, 1000a, 1000b, 1000c) as function of time based on the received thermal images; determining a first derivative (1001, 1001a, 1001b, 1005) of the temperature response signal (1000, 1000a, 1000b, 1000c); and determining a level of blockage of the at least one internal cooling passageway (110, 120) based on the first derivative (1001, 1001a, 1001b, 1005) of the temperature response signal (1000, 1000a, 1000b, 1000c) wherein an unblocked blockage level is associated with image pixels by: identifying image pixels having a positive derivative peak of the first derivative (1001, 1001a, 1001b, 1005) immediately followed in time by a negative derivative peak of the first derivative (1001, 1001a, 1001b, 1005) as corresponding to an airflow onset time period, wherein both derivative peaks (1007, 1009) have an amplitude greater than a first threshold peak value; having a negative derivative peak of the first derivative (1001, 1001a, 1001b, 1005) immediately followed in time by a positive derivative peak of the first derivative (1001, 1001a, 1001b, 1005) as corresponding to an airflow shut-off time period, wherein both derivative peaks (1007, 1009) have an amplitude greater than a second threshold peak value; wherein a difference between the identified positive derivative peaks and the negative derivative peaks for the onset time period and the shut-off time period is greater than a third threshold value; and having the first derivative (1001, 1001a, 1001b) of the temperature response signal (1000, 1000a, 1000b) that returns to within an equilibrium range of zero within a threshold number of image acquisition frames. receiving a continuous sequence of thermal images of at least an exit hole defined by the at least one internal cooling passageway (110, 120) at a surface of the turbine component; delivering a pressurized airflow pulse at a stable temperature into the at least one internal cooling passageway (110, 120) of the turbine component, the turbine component at the thermal equilibrium state with its surrounding environment; receiving a temperature response signal (1000, 1000a, 1000b, 1000c) as function of time based on the received thermal images; determining a first derivative (1001, 1001a, 1001b, 1005) of the temperature response signal (1000, 1000a, 1000b, 1000c); and determining a level of blockage of the at least one internal cooling passageway (110, 120) based on the first derivative (1001, 1001a, 1001b, 1005) of the temperature response signal (1000, 1000a, 1000b, 1000c) wherein an unblocked blockage level is associated with image pixels by: identifying image pixels having a positive derivative peak of the first derivative (1001, 1001a, 1001b, 1005) immediately followed in time by a negative derivative peak of the first derivative (1001, 1001a, 1001b, 1005) as corresponding to an airflow onset time period, wherein both derivative peaks (1007, 1009) have an amplitude greater than a first threshold peak value; having a negative derivative peak of the first derivative (1001, 1001a, 1001b, 1005) immediately followed in time by a positive derivative peak of the first derivative (1001, 1001a, 1001b, 1005) as corresponding to an airflow shut-off time period, wherein both derivative peaks (1007, 1009) have an amplitude greater than a second threshold peak value; wherein a difference between the identified positive derivative peaks and the negative derivative peaks for the onset time period and the shut-off time period is greater than a third threshold value; and having the first derivative (1001, 1001a, 1001b) of the temperature response signal (1000, 1000a, 1000b) that returns to within an equilibrium range of zero within a threshold number of image acquisition frames. identifying image pixels having a positive derivative peak of the first derivative (1001, 1001a, 1001b, 1005) immediately followed in time by a negative derivative peak of the first derivative (1001, 1001a, 1001b, 1005) as corresponding to an airflow onset time period, wherein both derivative peaks (1007, 1009) have an amplitude greater than a first threshold peak value; having a negative derivative peak of the first derivative (1001, 1001a, 1001b, 1005) immediately followed in time by a positive derivative peak of the first derivative (1001, 1001a, 1001b, 1005) as corresponding to an airflow shut-off time period, wherein both derivative peaks (1007, 1009) have an amplitude greater than a second threshold peak value; wherein a difference between the identified positive derivative peaks and the negative derivative peaks for the onset time period and the shut-off time period is greater than a third threshold value; and having the first derivative (1001, 1001a, 1001b) of the temperature response signal (1000, 1000a, 1000b) that returns to within an equilibrium range of zero within a threshold number of image acquisition frames.