A method of monitoring the operation of a device comprising a plurality of detectors (40, 42, 44, 46, 48) that provide respective indications of operational parameters that are indicative of an operation condition of the device, the method performed by a processor, performing the steps of: A: determining a plurality of operational parameters that are indicative of an operation condition of the device; B: determining a difference between each determined operational parameter and a corresponding limit on the operational parameter, each limit indicating a value of the corresponding operational parameter that corresponds to an undesirable operation condition of the device, and determining an Euclidean distance of each determined operational parameter from the corresponding limit, wherein the determined Euclidean distance is the determined difference, and wherein step B further comprises determining the Euclidean distance squared for each determined operational parameter; characterized by the following steps: C: determining an action index based on a smallest one of the determined differences, wherein step C comprises establishing a modified operational parameter for the operational parameter having the smallest determined difference by adding a weighted version of the determined difference for the operational parameter to the determined operational parameter and determining a modified difference between the established modified operational parameter and the corresponding limit and wherein step C further comprises determining the action index by multiplying the matrix of the modified difference by a principal component vector matrix by a diagonal matrix of principal component Eigen values by a transpose of the principal component vector matrix by a transpose of the matrix of the modified differences, wherein the principal component vector matrix includes predetermined operational parameter values corresponding to desirable operation of the device, and the action index comprises a shutdown index indicative of a need to take action to shutdown operation of the device; and D: determining whether the action index is within a range corresponding to desirable operation of the device, wherein step D further comprises establishing a lower limit on an acceptable value for the action index and providing an indication that action should be taken when the action index has a value less than the lower limit. A: determining a plurality of operational parameters that are indicative of an operation condition of the device; B: determining a difference between each determined operational parameter and a corresponding limit on the operational parameter, each limit indicating a value of the corresponding operational parameter that corresponds to an undesirable operation condition of the device, and determining an Euclidean distance of each determined operational parameter from the corresponding limit, wherein the determined Euclidean distance is the determined difference, and wherein step B further comprises determining the Euclidean distance squared for each determined operational parameter; C: determining an action index based on a smallest one of the determined differences, wherein step C comprises establishing a modified operational parameter for the operational parameter having the smallest determined difference by adding a weighted version of the determined difference for the operational parameter to the determined operational parameter and determining a modified difference between the established modified operational parameter and the corresponding limit and wherein step C further comprises determining the action index by multiplying the matrix of the modified difference by a principal component vector matrix by a diagonal matrix of principal component Eigen values by a transpose of the principal component vector matrix by a transpose of the matrix of the modified differences, wherein the principal component vector matrix includes predetermined operational parameter values corresponding to desirable operation of the device, and the action index comprises a shutdown index indicative of a need to take action to shutdown operation of the device; and D: determining whether the action index is within a range corresponding to desirable operation of the device, wherein step D further comprises establishing a lower limit on an acceptable value for the action index and