Scientists identify the most effective tools for capturing airborne microbes in indoor environments

Indoor air contains countless microscopic particles, including bacteria and viruses that can affect human health. A new study from the Jiangsu Center for Disease Control and Prevention provides the most detailed comparison to date of four commonly used microbial aerosol samplers. The findings offer practical guidance for researchers and public health agencies working to monitor airborne pathogens in homes, hospitals, schools, and other indoor spaces.

The study evaluated how effectively each device captured simulated microbial aerosols that matched the size of many respiratory pathogens. These included fluorescent microspheres measuring 0.3 micrometers and 1 micrometer, which served as surrogates for virus and bacterial particles. Experiments were conducted in a controlled stainless steel environmental chamber that ensured stable airflow, temperature, and humidity.

“Our results show that the membrane filtration sampler consistently achieved the highest collection efficiency for particles at or below one micrometer,” said lead author Yuanyuan Zhu. “Understanding which tools perform best under different indoor conditions is essential for improving microbial air monitoring and supporting public health protection.”

Four widely used aerosol samplers were tested: a membrane filtration sampler, a liquid impinger, a dry wall cyclone, and a wet wall cyclone. For the liquid based devices, the researchers also examined how different sampling media influenced performance, comparing phosphate buffered saline, RNase free water, and irradiated physiological saline. Each sampler processed two thousand liters of air under multiple flow conditions.

Across all experiments, the membrane filtration sampler produced fluorescence intensities four to ten times higher than the other devices. This indicates substantially higher capture efficiency for both virus sized and bacteria sized surrogate particles. The study also showed that higher flow rates improved the performance of the membrane filtration sampler, with peak efficiency observed at a flow rate of fifty liters per minute.

Zhen Ding, the senior author of the study, emphasized the practical value of the findings. “Choosing the right sampler directly affects the accuracy of airborne pathogen detection,” Ding said. “Our work provides evidence based guidance for field teams who conduct air surveillance, especially in settings where microbial concentrations are low and sample loss can occur easily.”

Among the liquid based samplers, phosphate buffered saline produced the highest fluorescence signals and therefore the strongest collection performance. This effect was particularly pronounced for bacterial sized particles. The authors note that phosphate buffered saline helps maintain stable pH and improves dispersion of microspheres, which supports more efficient particle recovery.

The results also revealed that extremely high airflow can reduce the performance of wet wall cyclone samplers. At very high flow rates, evaporation of the collection liquid and re aerosolization of particles can occur, lowering the amount of material captured. This finding underscores the importance of balancing flow rate with liquid stability in real world sampling.

While the membrane filtration sampler captured the highest number of submicron particles, the researchers stress that physical capture efficiency does not always predict biological recovery. Microbial viability can be affected by dehydration or stress during sampling. Further studies will evaluate how well each device preserves the integrity of living bacteria and viruses.

Overall, the study demonstrates that membrane filtration is the most efficient method for mechanical collection of airborne particles at or below one micrometer under controlled indoor conditions. The authors recommend its use for applications requiring rapid and sensitive detection. They also encourage future field based validation to confirm how sampler performance translates to real buildings where ventilation, sunlight, and human activity can influence results.

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Journal reference: Zhu Y, Peng S, Xu B, Ma K, Yang H, et al. 2025. Efficiency and performance of microbial aerosol samplers: insights from a controlled chamber study. Biocontaminant 1: e012  

https://www.maxapress.com/article/doi/10.48130/biocontam-0025-0011  

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About Biocontaminant:
Biocontaminant is a multidisciplinary platform dedicated to advancing fundamental and applied research on biological contaminants across diverse environments and systems. The journal serves as an innovative, efficient, and professional forum for global researchers to disseminate findings in this rapidly evolving field.

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