The disclosure relates to a safety device and a method for detecting and evaluating the degree of attention of an operator of a technical installation or a technical process, which includes a first module which records values of predefined physiological parameters of the operator and determines a first characteristic number from the recorded values, compares the determined first characteristic number with a predefined first characteristic value, which activates a second module which records further values provided by a checking or triggering mechanism. The second module determines a second characteristic number for the degree of attention of the operator from the recorded further values, compares the second characteristic number with at least one second predefined characteristic value, which triggers an activation module in order to take countermeasures which increase the attention of the operator of the installation.