Aerosol tracer testing in Boeing 767 and 777 aircraft to simulate exposure potential of infectious aerosol such as SARS-CoV-2

Abstract

The COVID-19 pandemic has reintroduced questions regarding the potential risk of SARS-CoV-2 exposure amongst passengers on an aircraft. Quantifying risk with computational fluid dynamics models or contact tracing methods alone is challenging, as experimental results for inflight biological aerosols is lacking. Using fluorescent aerosol tracers and real time optical sensors, coupled with DNA-tagged tracers for aerosol deposition, we executed ground and inflight testing on Boeing 767 and 777 airframes.Analysis here represents tracer particles released from a simulated infected passenger, in multiple rows and seats, to determine the exposure risk via penetration into breathing zones in that row and numerous rows ahead and behind the index case. We completed over 65 releases of 180,000,000 fluorescent particles from the source, with 40+ Instantaneous Biological Analyzer and Collector sensors placed in passenger breathing zones for real-time measurement of simulated virus particle penetration.Results from both airframes showed a minimum reduction of 99.54% of 1 µm aerosols from the index source to the breathing zone of a typical passenger seated directly next to the source. An average 99.97 to 99.98% reduction was measured for the breathing zones tested in the 767 and 777, respectively. Contamination of surfaces from aerosol sources was minimal, and DNA-tagged 3 µm tracer aerosol collection techniques agreed with fluorescent methodologies.

COVID-19 in the Airline Industry: The Good, the Bad, and the Necessary

“…29 In their subsequently published peer-reviewed article, the authors said that "[c]onclusions outside of specifically tested seats and breathing zones assumes extrapolation of the data to new conditions." 30 Still, these finer points are not reflected in the results of a Google search about this study which include a long list of headlines like, "It's almost impossible to get COVID-19 on an airplane. "…”

“…To their credit, the authors of the TRANSCOM-commissioned study published a post-script to their online report, which acknowledged that the impact of human behavior on aerosol transport, such as “[m]ovement of people up and down the aisles or even simply the act of turning your head to talk to your neighbor,” had not been considered. 29 In their subsequently published peer-reviewed article, the authors said that “[c]onclusions outside of specifically tested seats and breathing zones assumes extrapolation of the data to new conditions.” 30 Still, these finer points are not reflected in the results of a Google search about this study which include a long list of headlines like, “It's almost impossible to get COVID-19 on an airplane.”…”

“…When worn consistently and properly, masks have been shown to at least mitigate the risk of infection via the airborne route on aircraft. 30,31 It has been suggested that, in addition to trapping some virus particles by impaction, masks may add protection by increasing the humidity of the wearer's inhaled air. 32 So, given the enclosed and crowded nature of the cabin with higher bioeffluent concentrations, low humidity, and at least some forward and backward motion of air, masks provide an important line of defense.…”

Characterization of the indoor near-field aerosol transmission in a model commercial office building

“…To positively identify NaCl aerosols against the background indoor or outdoor aerosols with the same size, the NaCl aerosol was tagged with uranine (Fluorescein sodium salt, MW = 376.27 g mol −1 ; C 20 H 10 Na 2 O 5 , CAS#: 518-47-8; Sigma Aldrich) to provide a unique fluorescent signal for aerosol characterization from the ambient environmental aerosol. Similar tagging technology has been used to understand indoor aerosol transmission in aircraft [ 12 ].…”

Characterization of the indoor near-field and far-field aerosol transmission in a model commercial office building

“…To positively identify generated aerosols against the background indoor aerosols or aerosols from the OA with the same size, Uranine (Fluorescein sodium salt; MW= 376.27 g mol -1 ; C 20 H 10 Na 2 O 5 ; CAS#: 518-47-8; Sigma Aldrich) was tagged into the sodium chloride aerosol to provide a unique fluorescent signal for aerosol characterization from the ambient environmental aerosols. Similar tagging technology has been used to understand indoor aerosol transmission in aircraft (Kinahan et al, 2021). The nebulization solution was prepared by dissolving 3 g NaCl and 1 g Uranine into 400 mL Nanopure water.…”