Microbial contamination of air in two air conditioning systems and improvement effect with duct cleaning

HVAC systems in two hotel buildings in Pyongyang have been surveyed from 1997 to 2002 to check the effectiveness of combined mechanical cleaning and duct disinfections against microbial contamination..There were many differences of microbial contamination between the two HVAC systems during 1997-1998. respectively for bacteria and fungi in the air outlet . But they decreased from 45.9 and 28.7 cfu/m3 during 1997-1998 year to 10.3 and 4.5 cfu/m3 during 1999-2002 year