A control mat monitoring and warning apparatus and method in which the resistance of a control mat is monitored continuously while the mat remains in use. Deviations of the pattern of control mat resistance values in use from a nominal range of acceptable values is used to detect and report deterioration of the electrical performance characteristics of the control mat so that the mat can be removed from service and replaced in a timely manner. The disclosed invention also generates proper presence detection signals by compensating for the deteriorating electrical performance characteristics of the control mat, thereby extending the useful functional life of the control mat beyond the point at which the mat could otherwise function properly.