Abstract:

Objective To investigate the hygiene status of central air conditioning ventilation systems in public places in Haidian District of Beijing and to provide a basis for standardizing hygiene management. Methods From 2023 to 2024，fifty central air conditioning ventilation systems from public places were tested for hygiene indicators，including supply air，the inner surface of air ducts，and Legionella pneumophila in cooling water，and the data obtained were analyzed. Results The overall qualified rate for the 8 hygiene indicators was 95.6%. The qualified rates for total bacterial count of supply air，total fungal count of supply air，dust accumulation in the inner surface of air ducts，and Legionella pneumophila in cooling water were 72.0%，84.0%，99.2%，and 60.0%，respectively. The remaining indicators（inhalable particulate matter and β-hemolytic Streptococcus in supply air，total bacterial count and total fungal count in the inner surface of air ducts） all reached 100.0%. From the perspective of locations，the overall qualified rate for medical institutions was 96.6%，significantly higher than the 93.9% for non-medical institutions（χ²=3.915，P<0.05）. The qualified rate for Legionella pneumophila in cooling water of medical institutions was 71.9%，significantly higher than the 38.9% for non-medical institutions（χ²=5.223，P<0.05），and the main serogroups of Legionella pneumophila in medical and non-medical institutions were Lp1 and Lp2-14，respectively（P<0.05）. From the perspective of hygiene indicators，there were statistically significant differences among the inhalable particulate matter，total bacterial count，total fungal count，and β-hemolytic Streptococcus in supply air（χ²=28.396，P<0.01）. The total bacterial count in the inner surface of air ducts was positively correlated with dust accumulation and the total fungal count（r=0.491，0.556，both P<0.01），and the total bacterial count of supply air was also positively correlated with the total bacterial count and total fungal count in the inner surface of air ducts（r=0.413，0.316，both P<0.05）. Conclusion The overall hygiene status of central air conditioning ventilation systems in Haidian District of Beijing is satisfactory. However，attention should be paid to bacterial and fungal levels in supply air and Legionella pneumophila in cooling water，enhancing routine cleaning and disinfection.

Key words: Public place, Central air conditioning ventilation systems, Hygiene status, Total bacterial count, Total fungal count, Legionella pneumophila