Abstract: Objective To analyze the influencing factors of microbial purification efficiency of the air supply cabinet in the centralized air conditioning ventilation system of Wuhan Metro,explore technical methods to improve the quality of pipeline air supply. Methods From 2021 to 2023,32 centralized air conditioning ventilation systems were randomly selected and divided into experimental group(condensate pool with water sealing) and control group(condensate pool without water sealing) according to 1 ∶ 1 ratio. Under normal operating conditions of the centralized air conditioning ventilation system,the microbial concentration was detected in the exhaust air of the electrostatic sterilizer at the front end,back end,and end of the pipeline of the wind turbine cabinet. Results (1)In the three years from 2019 to 2021,the purification rates of total bacterial count in the air supply of the air cabinet were 94.94%,95.56% and 90.76%,respectively. There was no statistically significant difference in the concentration levels of total bacteria in the annual air supply before and after purification(χ²_{before purification}=3.304,χ²_{after purification}=4.405,all P>0.05),and there was no statistically significant difference in purification rate(χ²=2.673,P>0.05). The purification rates of total fungi in the air supply of the air cabinet were 94.89%,91.35%,and 88.35%,respectively. There were statistically significant differences in the concentration levels of total fungi in the annual air supply before and after purification(χ²_{before purification}=6.538,χ²_{after purification}=6.514,all P<0.05),and there was no statistically significant difference in purification rate(χ²=1.818,P>0.05). The concentration level of total fungi in the air supply before and after purification was the highest in 2021.(2)In control group and experimental group,the purification rates of total bacterial in the air supply of the air cabinet were 93.80% and 97.70%,respectively. There was no statistically significant difference in the concentration level of total bacteria in the air supply before purification(Z=-0.339,P>0.05), but there was a statistically significant difference in the concentration level of airborne total bacteria after purification(Z=-2.005,P<0.05),and the difference in purification rate was also statistically significant(Z=-2.828,P<0.05). The experimental group had a lower concentration of total bacteria in the air after purification. The purification rates of total fungi in the air supply of the air cabinet were 89.25% and 95.50%,respectively. There was no statistically significant difference in the concentration level of total fungi in the air supply before purification(Z=-1.753,P>0.05),but there was a statistically significant difference in the concentration level of airborne total fungi after purification(Z=-3.226,P<0.05),and the difference in purification rate was also statistically significant(Z=-2.789,P<0.05). The experimental group had a lower concentration of total fungi in the air after purification.(3) There was no statistically significant difference in the concentration level of total bacteria in the air supply of the centralized air conditioning pipe end between control group and experimental group(Z=-1.008,P>0.05),and the qualified rates of air supply outlets were 93.75% and 100.00%,respectively. There was a statistically significant difference in the concentration level of total fungi in the air supply(Z=-3.989,P<0.05),and the qualified rates of air supply outlets were 68.75% and 93.75%,respectively. The concentration level of air supply total fungi at the end of central air conditioning pipe was lower in experimental group. Conclusion The electrostatic sterilizer for centralized air conditioning in Wuhan Metro has a relatively stable purification efficiency for air microorganisms,but the concentration level of microorganisms after purification is greatly affected by the quality of the air source. The condensate pool of the centralized air conditioning and ventilation system fan cabinet can effectively block outdoor environmental pollution to the fan cabinet when in a water sealed state,and improve the quality of pipeline air supply.

Key words: Central air conditioning ventilation system, Purification efficiency, Electrostatic sterilizer, Condenser pool, Air supply microorganisms