BTW
B752PCF has a Fire Extinguishing system in the Bulk cargo holds unlike the B752SF.
Also the LH recirulation fan is located just aft of the FD panels & upstream of the OEV [Overboard exhaust valve].If the LH Recirulation fan is running it will provide the flow to clear the smoke through the OEV.
The RH Recirulation fan is NOT present on the B757 Freighter as its not serving the purpose.