As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON ENTERING CABIN NOTICED STRONG ACRID ODOR & A HAZE IN THE CABIN THE RECIRC FAN SWITCH WAS ON WITH NO AIRFLOW FROM PASSENGER VENTS. REMOVED RECIRCULATION FAN IAW AMM TASK 21-22-16-000-801. FOUND RED SHOP RAG LODGED IN RECIRC FAN INTAKE. INSPECTED DOWNSTREAM DUCTING AND ADJACENT AREAS FOR EVIDENCE OF TORN RAG. NO DEFECTS NOTED. INSTALLED A SERVICABLE RECIRC FAN FROM STOCK IAW AMM TASK 21-22-16-400-801. OPS TEST IS GOOD. RETURNED TO SERVICE.