ABSTRACT
Objective @#To systematically evaluate the detection of Legionella pneumophila in central air-conditioning systems of public places in China, so as to provide insights into the management of L. pneumophila contamination.@*Methods@#The publications pertaining to L. pneumophila contamination in central air-conditioning systems of public places in China were searched in international and national databases, including CNKI, Wanfang Data, CBM, PubMed and Web of Science from January 1, 2010 to December 31, 2022. The publication quality was evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology. A meta-analysis was performed using the software Stata version 16.0. The pooled detection of L. pneumophila and its 95%CI were estimated. The publication bias was evaluated using Begg's test, and sensitivity analysis was performed with the leave-one-out evaluation for assessment of the robustness of the outcomes.@*Results@#A total of 742 publications were initially searched, and 29 publications were finally included, all of which were cross-sectional studies. The publications included 10 high-quality and 19 moderate-quality studies covering 6 160 samples, and the pooled detection of L. pneumophila was 17.20% (95%CI: 12.80%-21.90%). Subgroup analysis showed a higher detection rate of L. pneumophila in cooling water (21.80%) than in condensed water (5.50%) (P<0.01). According to the criteria defined in Hygienic Specification of Central Air-conditioning Ventilation System in Public Buildings (2006 version), the detection of L. pneumophila was 23.30%, which was higher than the detection (13.20%) according to the Hygienic Specification of Central Air-conditioning Ventilation System in Public Buildings (WS 394-2012) (P<0.05). The detection of L. pneumophila did not vary in place, region or sample (P>0.05). Begg's test showed no significant publication bias, and sensitivity analysis showed robustness of the results. @*Conclusions@#The detection of L. pneumophila ranges from 12.80% to 21.90% in central air-conditioning systems of public places in China. Health and environmental protection sectors need to improve the monitoring of L. pneumophila contamination in central air-conditioning systems of public places.
ABSTRACT
Objective A correlation method for evaluating operation quality of air conditioning systems is proposed , based on the outdoor and the indoor temperature history data of the terminal user from internet of things for the central air conditioning system , for lacking efficient way to evaluate . Methods A methematical model is set up based on the variance ratio of the data of the indoor and out temperture obtained from IOT within a given time interval , and theoretically induce the possibility and correctness to employ these index to evaluate the operation quality of the central air conditioning system . Results A typical central air conditioning system of a large sacal hospital is analyzed , the results shows the variance ratio of the indoor and outdoor temperature can reflect the capacity of the central air conditioning system for controlling the indoor temperature . Conclusion The method proposed for evaluating the op-eration quality of the air conditioning system based on IOT system is theotically correct and practically efficient , and can be employed to evaluate the operation quality of the air conditioning system of large scale medical buildings .
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Objective To konw the Legionella contamination in the central air condition system and secondary water supply system in the public places of Jiangxi province. Methods 145 water samples were collected from the public places with central air conditioning system and secondary water supply system, in July to September in 2005-2006. Bacteria culture, hemagglutination test and duplex PCR test were used to identify Legionella. Results 15 Legionella strains was isolated from 145 samples, the positive rate was 10.34%, 7 Legionella strains was isolated from 78 samples of central air conditioning system, the positive rate was 8.97%, 8 Legionella strains was isolated from 57 samples of secondary water supply system,the positive rate was 14.04%. Conclusion It is necessary to strengthen the surveillance of Legionella in central air conditioning system and secondary water supply system.
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Objective To verify the flow field performance of the air dynamic wind tunnel. Methods The performance of the flow field was evaluated by testing the flow speed of sample-point on the sample-transect of the tunnel. Results Among the flow range of the tunnel, the relative deviations of the speeds of each sample-point on the sample-transect were less than 10%. When the flow rate was set, the relative deviations of the sample-transect average speed in different test period were less than 10%. The ratio of average wind velocity of upper reach to down reach of the tunnel was between 0.92 and 1.03. Conclusion The flow field of the air dynamic wind tunnel is even, stable and coincident.
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Objective To explore the transmission route of Legionella pneumophila in central air-conditioning system. Methods The environmental samples collected from four public places of Nanjing city were detected by nested-PCR and analyzed by phylogenetic analysis. Results The positive rate of Legionella pneumophila in sediment, cooling water, aerosol near cooling tower, dust in duct surface and indoor air were 100%(9/9),78.6% (11/14),25.4% (17/67),16.7% (2/12) and 17.3% (13/75), respectively. The nucleotide sequence similarities of Legionella pneumophila in cooling water and indoor air was more than 92%. Conclusion The main pollution source of Legionella pneumophila is cooling water and Legionella pneumophila can be transmitted to indoor air through central airconditioning system.
ABSTRACT
Objective To know the hygienic administration status of central air conditioning system(CACS)and the Legionella contamination of cooling water in public places; and to identify the risk factors for legionella contamination associated with hygienic administration measures of CACS. Methods One hundred and forty-eight public places with CACS were recruited and the hygienic administration status was investigated by questionnaire survey in Sep. 2008. The culture methods were used to identify Legionella in cooling water. Results Positive rate of Legionella pneumophila in cooling water was 68.1%, 65.1% and 66.7% respectively in the condition of disinfection, preservative (detergent) and regular examination of the cooling water. The positive rate of Legionella pneumophila in cooling water was 92%, 87.7% and 84.7% respectively without disinfection, preservative,detergent and regular examination of the cooling water. Conclusion Disinfection, preservative,detergent and regular examination of the cooling water can reduce Legionella contamination risk.