A system for in line in situ validation of an air filter of an exhaust filter system including a scan head, a means for facilitating movement of said scan head in the XY plane, a means for externally controlling the movement of the scan head from outside the plenum of the exhaust filter system in the XY plane, and a means for coupling the scan head to the means for externally controlling the movement of the scan head, is provided. The system can also include a scanning arm, inside and outside magnetic couples, and rolling means to facilitate movement of the inside and outside magnetic couples. A method for in line in situ validation of an air filter in an exhaust filter system is also described, which involves the use of the system for in line in situ validation of air filters of an exhaust filter system.