In this recorded conference session (Tech Seminar 2022), David Space (former Boeing engineer) spoke about the airplane operating environment, how an airplane Environmental Control System (ECS) works, air filtration advancements over time, and how the air distribution system and airplane design features control for air quality and spread of disease.
Review the slides: ⁠https://amped.egnyte.com/dl/LEPxPrUWAK⁠
For detailed show notes, read below and use the timestamps
to navigate the episode: 
[2:01] David describes the airplane operating environment and how an environmental control system has multiple functions, such as maintaining cabin pressure anti-icing systems, cargo heat, and ventilation. 
[3:00] David describes how an ECS system continuously circulates outside air when it enters the engine and into a mixing chamber, where it is mixed with recirculated air. This 50/50 mix is distributed to the cabin and exits the airplane through valves.  
[4:33] David begins his review of the history of air filtration and advancements in aircraft with the Boeing Stratoliner, the first aircraft to implement air recirculation in 1945. After that, NASA research led to the application of HEPA filters for recirculated air, allowing for less fuel waste without compromising the quality of the cabin air. David Space participated in this research in 2002 and expanded on carbon air purification and filter capture methods for HEPA research in 2015 at the Lawrence Berkeley National Labs.  
[7:28] David Space analyzes a graph comparing airplane filtration to filtration in other modes of transportation and in environments such as hospitals and office buildings.  
[8:18] What do the latest statistics show on the spread of disease? The industry was hit hard by the COVID-19 pandemic; international flights dropped by 75% in 2019, and few reports on the spread of COVID during flights were available. 
[9:50] The Department of Defense used United Airlines for an eight-day study with four days on the ground and four days in flight. Mannequins released particles in the air with simulated coughing and breathing mechanisms. Decay, also known as how soon the particles leave the cabin, occurred much quicker due to a higher air exchange rate. 
[15:21] David compares the ASHRAE 1262 in-flight research to another study he was a part of with American Airlines on the factors that affect comfort for passengers while in flight. They took this data to the Technical University of Denmark for more human subject research on air quality. They found that air purification could raise humidity and lower gaseous contaminants. David’s research continues at Rutgers to find that bio effluents are the primary contaminant due to the high density of people. 
[21:17]
David presented actual measurements collected during flights across the Boeing fleet, indicating that the 787 has lower volatile organic compounds. The FAA adopted prescriptive regulations for ventilation systems, but David believes performance-based regulations would be better. He
suggested implementing filtration systems to handle particulate matter and gaseous contaminants, which would improve passenger comfort and reduce engine emissions.

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