A Risk Assessment of an Airborne Disease inside the Cabin of a Passenger Airplane
Abstract:
Analytical calculations along with computational fluid dynamic (CFD) simulation of a Boeing 737-600 cabin with a single infector (a passenger) has been performed using a passive scalar gas with particle sizes similar to the sizes of influenza virus laden particles which are assumed to be comparable to the sizes of the Coronavirus laden particles. CFD results of the virus transport and concentration were used in conjunction with the Wells-Riley (WR) quanta estimation from two well-documented cases of influenza infection on airplanes (with the assumption that the infections were primarily from the airborne route), to estimate the infectious rate. The risk of infection is estimated by the quanta of viruses inhaled assuming 0.3 CFM of passive scalar gas corresponds to 1267 viruses/minute released. Results indicate that with a 3-hour flight, the risk of infection is nearly 50% for those sitting in the vicinity of the infector which is equal to 2-3 infections for 131 passengers.
A comparison to a documented COVID-19 case shows that 4 symptomatic passengers could infect 2 others if the COVID-19 virus infectiousness lays mid-range of the influenza infectious doses.
The use of masks could dramatically reduce the risk of airborne infection. When the infector wears a mask the virus concentration is reduced for all other passengers and the mask is more effective at catching the virus droplets before they dry out in the cabin air. A significant reduction in virus transport and the infectious rate was observed with the N95 mask for a 3-hour flight.
With 2.9-ft social distancing (vacant middle seat) resulting in 2/3 cabin passenger capacity, the ventilation rate per person is increased by 45% and the risk of infection was dropped by more than 48%.