Objective To investigate the effect of washing central air conditioning system on human health.

Method Subjective feeling of employees in two hotels and their health examination data were collected and analyzed before and after the central air conditioning systems being cleaned in 2012.

Results The full mark rate estimated by employees on the indoor air quality in workplace was increased significantly after cleaning. The symptoms such as dry skin, pruritus and redness of skin and the feeling of insomnia or drowsiness were improved; the sensation of nasal stimulus, nasal congestion or running nose caused by the environment in the hotel was significantly improved; and the signs of cough, expectoration, chest distress and shortness of breath, as well as fatigue or not concentrating were improved after the central air conditioning system being cleaned.

Conclusions The degree of satisfaction to indoor air quality in workplace estimated by employees was significantly increased after cleaning. Cleaning centralized air ventilation system can improve human health.