Thread by @ARISense_AQ

#AAAR2022 Aerosol Dispersion of Submicrometer Particles in an Aircraft Cabin. Stephanie Vannarath, Peter Kim, Mitchell Ford, Arvind Santhanakrishnan, Yu Feng, CHANGJIE CAI, The University of Oklahoma Health Sciences Center

Airplane cabins! Oh boy.. excited for this one.

infectious aerosols exist. Particularly interested in submicron ones - deep in our respir. tract. Travel further. Remain airborne longer. For the same mass, they have higher surface area.

Settling times of different particles 1 um. They can be suspended in the air for 9h.

1.16m height suspension assumption. 9h. 9h people.

Motivation: air travel implications of COVID. huge economic losses.

People get on airplanes and they think a bit more about the air they are breathing.

This study was done in a real airplane. Which is awesome. N491 American Airlines MD-80. In this study we selected the main cabin as area of focus.

Ventilation system in the airplane, for most commercial jets have this air exchange of ~ 20. The air is come down from the top of the cabin and exists at the floor.

We can think about factors effecting dispersion. Over your seat there are some gas vents. How will these effect dispersion? Proximity.. to vent or to source (seated somewhere else)

Goal. Reduce the aerosol concentration by size in the cabin.

Evaluate the effectiveness of the vent system in the cabin.

Understand how much the gas vents matter?

OPC we used in this study was a GRIMM ~250 nm to 24 microns.

We used a Collison nebulizer to generate aerosols. Release these in the middle of the cabin - get to steady state concentration and then change vent conditions.

Collect the particle data at each seat. Across all rows and all seats.

First experiment - Everything is OFF.
2) Turn on ventilation.

Evaluate the effectivness of the vent system.

3,4,5 - we keep vent system on.

Sample 3 vent on/gas vents off

Sample 4 vent on/gas vents on

Sample 5 - vent on/gas vent on only over the source

Results - The ventilation is really only effective at reducing particles smaller than 0.5 microns.

Limitations... door wasn't totally sealed (not ideal).. hmmm - change that outdoor ambient aerosols impact the results. Interior dust could be generated during experiment.

300-400nm particles significant reduction

Larger stuff, not so much..

By turning on the gas vent fans you can significantly reduce the aerosol concentrations throughout the cabin.

Future work - CFD modeling - natural convection - each human is a heat source - if we consider natural convection air flow will go upwards. Both natural convection and gas vents - airflow patterns can change dramatically.

Nebullizer is making tons of particles. Humans don't breathe out nearly as many. Really need to consider lower particle generation and spread / and also adoption of PPE.

I still struggle with the "turn all the vents on full blast" strategy on the tarmac based on how much air pollution exhaust you then concentrate in the cabin.