AHU Requalification

My question is related to AHU Requalification.
consider a case where in AHU minor modification in dehumidifier is done or dehumidifier is changed.
In this case during requilification of AHU microbial testing of area or clean room is required or not?
In this case modification in AHU are done prior air passes through filters or pre filters kindly comments

Please mentioned the area classification, it is ISO - 8 its not required for microbiology monitoring, because of Dehumidifier modification, its done in service area, only air velocity, Particle count, differential pressure across the rooms and Temp&RH should be monitor, if the area is Grade A/B you should monitor microbiology also.