Abstract

Context In recent years, new commercial aircraft have been designed to recirculate approximately 50% of the cabin air to increase fuel efficiency. Some older aircraft use only fresh air. Whether air recirculation increases the transmission of infectious disease is unknown; some studies have demonstrated higher rates of the common cold among persons working in buildings that recirculate air.

Objective To evaluate the role of air recirculation as a predictor of postflight upper respiratory tract infections (URIs).

Design, Setting, and Participants A natural experiment conducted among 1100 passengers departing the San Francisco Bay area in California and traveling to Denver, Colo, during January through early April 1999, and who completed a questionnaire in the boarding area and a follow-up telephone interview 5 to 7 days later. Forty-seven percent traveled aboard airplanes using 100% fresh air for ventilation, and 53% traveled aboard aircraft that recirculated cabin air.

Main Outcome Measure Incidence of reporting new URI symptoms within 1 week of the flight.

Results Passengers on airplanes that did and did not recirculate air had similar rates of postflight respiratory symptoms. The rates of reporting a cold were 19% vs 21% (P = .34); a runny nose and a cold, 10% vs 11%, (P = .70); and an aggregation of 8 URI symptoms, 3% in both groups (P>.99). Results were similar after statistical adjustment for potential confounders.

Conclusion We found no evidence that aircraft cabin air recirculation increases the risk for URI symptoms in passengers traveling aboard commercial jets.

Aircraft cabins may be high-risk environments for transmission of infectious diseases. Space confinement, limited ventilation, prolonged exposure times, and recirculating air,4 all common to air travel, have been demonstrated to be risk factors for transmission of upper respiratory tract infections (URIs) in other settings. Several case reports detail outbreaks of influenza and tuberculosis aboard aircraft, but it is not known whether air recirculation increased rates of transmission. Air recirculation increases rates of transmission of viruses that cause the common cold in army barracks, but this possibility has not been studied in airplanes.

In the early 1980s, to enhance fuel efficiency, aircraft manufacturers began to build ventilation systems that recirculated cabin air. Older systems used 100% fresh air, compressed, humidified, and cooled by the engines in a process that consumed significant energy. Newer airplane models recirculate as much as 50% of cabin air, decreasing the engine’s work. The recirculated air passes through high-efficiency particulate filters before mixing with conditioned fresh air to reenter the passenger compartment. However, any filter’s ability to capture viruses is limited, even at peak function, and filters are rendered even less effective if bypassed, improperly used, or clogged by particulate matter.

Older aircraft that use only fresh air are being retired, and all new commercial aircraft are equipped to recirculate air. An evaluation of the differences between the effects of these 2 ventilation systems must be conducted before fresh air systems become obsolete. Our study aim was to evaluate the role of air recirculation as a predictor of postflight symptoms consistent with URIs. (…) Read Full Article Here

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