Characteristics of Legionella Pollution of Central Air Conditioning Ventilation Systems in Some Public Places of Hangzhou, 2013-2014

Objective To investigate the Legionella pollution in cooling water and condensate water of central air conditioning ventilation systems in public places of Hangzhou.

Methods A total of 30 cooling water samples and 30 condensate water samples were collected from 30 public buildings of Hangzhou in July and August from 2013 to 2014. Based on the Appendix A of the Hygienic Specification of Central Air Conditioning Ventilation System in Public Buildings (WS 394-2012), Legionella in water samples was tested, and the usage and management of the central air conditioning ventilation systems were also investigated.

Results The positive rates of Legionella in cooling water and condensate water were 33.33% (10/30) and 13.33% (4/30) respectively, and the 14 positive samples were all Legionella pneumophila positive. Longer service life of the central air conditioning ventilation systems was associated with greater Legionella positive rate (Z=1.794, P=0.036). The Legionella positive rate was statistically different between having cooling water sterilized (26.09%, 6/23) or not (100.00%, 7/7) (P=0.001).

Conclusion Serious and widely distributed Legionella pollution is found in the central air conditioning ventilation systems in public places of Hangzhou.