Poplar catkin contamination in vehicle air conditioning systems: Effects on filter performance, microbial survival,...

During the spring-to-summer transition, the poplar catkins pose a substantial challenge to cabin air filters, fundamentally distinct from conventional particulate matter pollutants such as dust. Once drawn into the air conditioning system, poplar catkins readily entangle in filter media, forming a dense layer that considerably increases pressure drop and promotes microbial survival. However, this dual challenge of accelerated clogging and microbial risk remains largely unexplored. In this study, microscopy and scanning electron microscopy (SEM) were employed to characterize used cabin air filters during the peak poplar catkin season. Field sampling and quantitative analysis were conducted to determine poplar catkin concentrations, as well as dust levels under different traffic conditions. A wind tunnel bench-scale test platform was established to systematically evaluate the dynamic pressure drop and particulate matter filtration efficiency of cabin air filters under three conditions: poplar catkin contamination alone, dust contamination alone, and combined contamination. The results indicate that poplar catkins and pollen not only physically clog cabin air filters but also transform them into potential microbial reservoirs, enhancing the survival rates of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by over 40% by providing nutrients and a humid microenvironment. This study proposes and evaluates a practical method for effectively slowing the rate of pressure drop increase in air conditioning systems by installing pre-filter materials at the air intake, and reducing bacterial survival and persistence by minimizing poplar catkin accumulation on cabin air filters.