Objective  To study the microbial contamination of central air conditioning ventilation system in public places, and to provide evidence for the standardization and supervision of these systems in public places.

Methods  According to the requirements of the Hygienic Specification for the Central Air Conditioning Ventilation System in Public Places (2006), the air and water samples were collected from 383 public places in a city in 2013—2015. The examination items were as follows: the total bacterial count, total fungi count and β－hemolytic streptococcus from the supplied air, along with the total bacterial count and total fungi count on the inner surface of air duct, as well as the Legionella pneumophila in cooling water and condensed water.

Results  The overall qualified rate of central air conditioning ventilation systems in 383 public places was 68.2% (261/383). The total qualified rates of bathing places, hotels and hospitals were 75.0%, 56.9% and 50% respectively. The qualified rates of total bacteria count and total fungi count in the supplied air were 93.4% (2324/2488) and 91.8% (2290/2495), respectively. The qualified rates of total bacteria and total fungi count on the inner surface of air duct were 97.1% (2400/2471) and 96.7% (2388/2469), respectively. In addition, the qualified rate of Legionella pneumophila in cooling water was 93.2% (618/663).

Conclusions  There was a microbial contamination in central air conditioning ventilation system of public places in the city in 2013－2015. The hygienic management of hotels and hospitals should be the priority field to be improved and strengthened. Furthermore, additional work should be done on revising examination indicators and optimizing evaluation system.