A321
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Flight Crew Overcame Equipment Problem; General Maintenance Action; General Flight Cancelled / Delayed
Aircraft
Arrived at Aircraft X; A321 at gate. APU was running. Selected APU bleed on as passengers started boarding around XA:30 and a strong fuel/oil odor filled the cockpit and the cabin. I turned the bleed back off and opened the windows in the flightdeck. I had the Flight Attendants stop boarding and get the 5-10 people that already got on; off the airplane. Then got the crew off and called Maintenance.
A321 Captain reported a fume event during boarding.