BC levels in the Beijing region are driven by large scale synoptic conditions. Air pollution control measures during the APEC Conference significantly reduced BC concentrations at both sites. Reductions in BC levels during the APEC Control Period were greater at the conference site than central Beijing. Winds from northwest and north had a purification impact on BC concentrations of both sites. The highest Huairou BC were associated with air masses from Central Beijing instead of the Hebei industrial areas.