Passengers are supposed to get clean and fresh air during a fight. So why is the air we breathe onboard airplanes so bad?

To really understand the quality of air you breathe inside that slim aluminium tube called an airplane, you don’t have to do much—you just have to ask the young people riding shotgun on the ladders, those who open the aircraft door. Feedback received ranges from stale and smelly to outright un-breathable and unsanitary. Every which way, the blast of what comes out from inside the airplane is so terrible, that those on duty outside instinctively turn away from it as the door is opened.
 
That this has only become worse over the last few decades is also a well-known secret. Especially when landing into extremely hot or cold ambient temperatures at airports. If the temperatures outside are comfortable, then to some extent, the fresh air permitted inside while taxiing would neutralise matters before doors were opened.
 
 But why is the air onboard airplanes so bad to begin with? Aren’t we supposed to be getting fresh and clean air, after all, there are billions of cubic metres of absolutely pure air right outside the portholes, all so carefully brought to a comfortable temperature and pressure over sea level  for us. As the announcement usually states. Lately, adept flyers may have noticed that airlines sometimes drop the information on temperature and cabin pressure in the  announcement, so much temperature outside and so much height over sea level inside, because some parts of it would worry the passengers.
 
Truth is, even the pilots don’t believe what they have to say about the air onboard anymore. More than a few deaths onboard as well as medical episodes being linked to the air onboard airplanes have made them very, very careful. 
 
What’s more worrying, however, is what the aviation industry has quietly done with the most important element of flying as a passenger, specifically, the air we breathe onboard. They simply let it go bad. In the name of fuel economy and higher profits, this is what happened with many “new generation” aircraft providing excellent fuel-efficient engines, thus proving once again that all new technology is not necessarily good for humanity.
 
Here’s what the new changes are:
1) They reduced the air pressure inside the airplane, moving up from 4,000 to 6,000 to around 8,000 and now often as high as 10,000 feet above Mean Sea Level (MSL), equivalent. Outside, at 35,000-40,000 feet above MSL, the air is much thinner, of course, and requires to be compressed. So, the lesser they need to compress, the lesser fuel they burn. Air pressure onboard can always be measured inside cabins with some very simple equipment, even easier now with people carrying portable computers to measure and keep records.
 
2) They simply did away with letting any really fresh cold air into the airplane at high altitudes, since that would also require fuel to heat. Instead, they now use air drawn through the hot engines (known as ‘bleed’, they can’t even get to calling it ‘air’ themselves), which is then mixed with the used air inside, forced through filters and cleaners, and then pumped right back into the cabin again. Air quality onboard can also be measured inside with some very simple equipment, and records kept on portable computers.
 
This mixture of stale air and ‘bleed’ is usually let into the aircraft in proportions that are pre-set by the airline and aircraft manufacturer, and the only parameter that is important to them, is fuel-cost saving. Even the least amount of fresh air allowed inside an aircraft flying at a high altitude would upset these fine calculations. So, typically, the pilot onboard has no say in adjusting these to try to improve air quality.
 
Somehow, for cockpit crew, the problem is solved by providing them with pure and fresh oxygen, if required. But that too can have disastrous results, as the yet unexplained crash of the Helios Boeing 737 Flight ZU-522, into a mountain in Greece, remains a mystery.
 
The filters and cleaners have to tackle a lot. In addition to used air, they also have to clean traces of a vast variety of chemicals and fuels, coming out of the jet engines. Imagine, then, for a moment that 100 of you are in a sealed air-con BEST bus, and that the air you breathe inside is a mix of the stale air and the air coming out of the exhaust, purified for you by expensive filters, mostly optional extras. Placed right next to the engine because, that’s right, it would save cost.
 
So now you are talking about filters and cleaners which need to be replaced very often. Since they cost a lot. Thousands of dollars, typically, and unlike your home air-conditioner filters—they can’t just be washed and re-installed. So, in this day and age of cost saving, and with nobody really watching, the filters and cleaners go on. For a long time.

And people keep falling sick. Or worse.
 
Till finally, some aviation crew, both cockpit and cabin, who get impacted the most because they are flying day in and day out—take the system head-on. In the UK, the US and Australia. And now they have some court judgements in their favour too.
 
More on toxic aviation air, soon, but meanwhile—please let us know —what are your experiences with air quality onboard airplanes, especially on long flights?
 
(This is the first part of a three-part series)