Air Quality During Flights - Does Recycled Air Spread Swine Flu on Flights?

Spreading Swine Flu / H1N1 Influenza

A big concern for many passengers when speaking of illnesses, not just Swine flu, but also other airborne illnesses, is the air quality during flights. The air is recycled (though airlines tend to prefer calling it "recirculated"), but what many passengers may not be aware of is how highly filtered that recycled air actually is.

So typically, what type of air filters are used on airplanes?
With the exception of some smaller or much older aircraft, airplanes are equipped with what are known as True High Efficiency Particle Filters (True HEPA) / High Efficiency Particle Filters (HEPA) filtration systems.

What do True High Efficiency Particle Filters (True HEPA) / High Efficiency Particle Filters (HEPA) filtration systems do?
These filtration systems recirculate air so that a complete air change occurs approximately 15-30 times per hour, or once every two to four minutes.

These systems can filter microscopic particles like bacteria and viruses. According to IATA, "HEPA filters are effective at capturing greater than 99 percent of the airborne microbes in the filter air. Filtered, recirculated air provides higher cabin humidity levels and lower particulate levels than 100% outside air systems."

How does this compare with other confined spaces?
This complete air change is better than most other forms of transportation and office buildings, and similar to hospitals.

What does this mean in terms of catching an illness on board a flight?
The risk of contracting something like a cold or flu on a flight should be lower than many other confined spaces because of the filters and air exchange - even though it may not seem to be the case, especially since cabin pressure can make a simple instance of the sniffles feel like a full-blown flu.