Dry heat steriliser validation

After completion of IQ , OQ then PQ .In PQ We need to perform as per protocol the parameters of 1.Air velocity 2.Hepa filter integrity report 3.Non viable particulate count test.
Before going to perform Non viable particle count test we need to run the blower 60 minutes (Heaters OFF condition) then
inside the chamber temperature shows 55°C. How to perform particle count test in these conditions
please give me suggestions