On all modern aircraft, passengers and crew breathe a mixture of fresh and recirculated air. Using this combination rather than fresh air only makes it easier to regulate temperature and helps maintain a bit of humidity (more on the humidity in a moment). The supply is bled from the compressor sections of the engines. Compressed air is very hot, but the compressors only compress; there is no contact with combustion gasses. From there it is plumbed into air conditioning units for cooling. It’s then ducted into the cabin through louvers, vents, and the eyeball gaspers above your seat. The AC units are known to pilots as “packs.” That’s an acronym for pneumatic air cycle kit. Usually there are two per plane.
The air circulates until eventually it is drawn into the lower fuselage, where about half of it is vented overboard—sucked out by the pressurization outflow valve. The remaining portion is remixed with a fresh supply from the engines and run through filters, and the cycle begins again.
Studies have shown that a crowded airplane is no more germ-laden than other enclosed spaces—and usually less. Those underfloor filters are described by manufacturers as being of hospital quality. I needn’t be reminded that hospitals are notorious viral incubators, but Boeing says that between 94 and 99.9 percent of airborne microbes are captured, and there’s a total changeover of air every two or three minutes — far more frequently than occurs in offices, movie theaters, or classrooms.
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If passengers have one very legitimate gripe, it’s about dryness. Indeed, the typical cabin is exceptionally dry and dehydrating. At around 12 percent humidity, it is drier than you will find in most deserts. This is chiefly a by-product of cruising at high-altitudes, where moisture content is somewhere between low and nonexistent. Humidifying a cabin would seem a simple and sensible solution, but it’s avoided for different reasons.
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None of this is disputing that people don’t occasionally become unwell from flying. While the air is clean, the dryness is bad for sinuses and can break down mucous barriers, making it easier to catch what bugs might be present. Usually, though, it’s not what passengers are breathing that makes them sick. It’s what they are touching: lavatory door handles, contaminated trays and armrests, etc. A little hand sanitizer is probably a better safeguard than the masks I occasionally see passengers wearing.
. But yeah you got a point, my excitement for the 3 is quite low tbh.
