Study: Air on planes cleaner than in most homes
Airborne spread on 767s, 777s was reduced 99.7%
A new study conducted for the Department of Defense adds credence to the growing belief that airline passengers face minimal risk of contracting coronavirus when flying.
The study found the risk of aerosol dispersion – transmission of the virus through the air – was reduced 99.7% thanks to high air exchange rates, HEPA-filtered recirculation and downward ventilation found on modern jets.
Investigators looked at the impact of an infected passenger on others seated in the same row and those nearby in the cabins of Boeing 767s and 777s. Those two aircraft types are widebodies typically used for long-haul flights where a virus would be expected to spread more easily.
To test the exposure risk for passengers sitting near an infected person, researchers released fluorescent tracer aerosols representing the droplets released by exhaling or coughing and looked at the impact on multiple “breathing zones” throughout the aircraft. In total, more than 11,500 breathing zone seat measurements were taken with releases from 46 different seats.
Asked about the report Thursday during a call with analysts and media, United CEO Scott Kirby said the results apply to other commercial jets as well.
“The reality is those tests are indicative of what happens on every airplane. An aircraft is just a remarkably safe environment.”
The study was conducted by a team that included members from United Airlines, Boeing, the University of Nebraska Medical Center, National Strategic Research Institute and research firms. It was prepared for two military agencies that move people and cargo, the U.S. Transportation Command and the Air Force’s Air Mobility Command.
The study is in keeping with the message that airlines have been trying to convey that HEPA filters and high turnover rates of airflow in passenger cabins reduce passenger exposure. In fact, the study found that contamination in the aircraft examined was less than what is found in private residences.
Kirby said with the airflow from ceiling to floor, “there is no place indoors that it is anywhere close to that” when it comes to limiting the spread. He urged other airlines to emulate United’s policy of making sure power units operate in a way that allows passengers to take advantage of aircraft ventilation systems while still at the gate.
He urged passengers to make sure that their overhead vents are fully open during their flights to maximize air circulation.
On most planes, the air exchange rate is approximately every three minutes and 75% comes from outside the plane, meaning that only 25% of cabin air is recirculated.
“The 767 and 777 both removed particulate 15 times faster than a home ... and five to six times faster than recommended design specifications for modern hospital operating or patient isolation rooms,” the study continued.
Tests were conducted by placing instruments that can measure particles in proximity to a simulated sick passenger. The study took masks into consideration, with a focus on the expectation passengers would be wearing surgical masks, the type most likely to be handed out by airlines in cases where passengers did not bring their own.
Studies are divided. Two studies published earlier this fall raised the prospect that the virus can spread between passengers, examining flights in which clusters of infections were reported.
It’s worth noting those studies involved flights that took place early in the pandemic. It was also unclear whether airlines had imposed some of the safety measures that later became adopted industrywide, such as mask requirements.
“An aircraft is just a remarkably safe environment.” Scott Kirby United CEO