Effect of selected sampling media, flow rate, and time on the sampling efficiency of a liquid impinger packed with glass beads for the collection of airborne viruses.

The liquid impingers can be used for sampling of viral aerosols, such as COVID-19 virus, influenza, and measles. However, the lowest cutoff diameter of commercially available liquid impingers was about 0.3 μm, and the physical collection efficiency for nano-bioaerosol is only about 10-20%. Here, we enhanced the impinger's collection efficiency and recovery of viable viral aerosols by using packed glass beads and selected sampling media (1% peptone and lysogeny broth, LB). Single-stranded RNA (ssRNA) MS2 bacteriophage with uranine (as a physical tracer) was used as model viral aerosols. The effects of different sampling flow rates (4, 6, and 12.5 L per minute) and different sampling time (10, 20, and 30 min) on the collection efficiency and recovery of MS2 aerosols were also tested. Collection efficiency and recovery of viable viral aerosols were analyzed as a function of sampling media, flow rate, and sampling time and packed glass beads by using a general linear model. Although the packed glass beads considerably enhanced the collection efficiency of the liquid impinger for MS2 aerosols, the recovery of viable MS2 becomes lower due to the higher pressure drop across the impinger. Using peptone or LB as sampling media, reducing sampling flow rate, and decreasing sampling time was proven to improve the recovery of viable MS2. Conclusively, this study provides some practical methods to improve the collection efficiency of liquid impinger for viral aerosols and preserve their viability.