Cabin air quality - Ozone or what?
 

This has to be one of the most enduring subjects in the public eye, airlines accused of recycling unhealthy bug infested, high CO2 air, yet nothing seems to be done about it.

Why is this ? On first reflection this appears very odd as there is a limitles supply of fresh air outside and all you need to do is scoop it in and heat it up to a cosy temperature. Easy.

What's the real reason then? Is it that at 40,000ft poisonous levels of Ozone are so high that scooping in outside air is a no no? Or does replenishing clean engine bleed air increase fuel burn or represent a power penalty i.e. real issues for the operators unlike passenge welfare?

Will current generation, 787 380, airplanes be better?

If you haven't got a cold or flu the chances are you will by the end of your next flight hopefully nothing worse

Because recycling the nasty, bug infected air is cheaper?

Less noisy and drafty? Anyway, the highest air circulation would be with open windows. :ok:

The problem is it's just too expensive to bring air in from outside and expel the stale air.

Boeing are trying to remedy this with the 787 - who knows, if they can do it, it might catch on..

There was some firm in the early '80s was interested in fitting
some sort of electronic plate to our DC8 air intakes with a view
to neutralizing the ozone coming in to the aircraft.
Unfortunately we went bust before anything was done about it.
Often wonder if anything was eventually fitted to ANY aircraft.
People were aware of the problem then.

The air recirculation system used on most modern aircraft just
helps to keep the fuel burn figures acceptably LOW.

The Air Is Fine Up Here
 

Um, well, lots of misconceptions regrading this subject remain...
Boeing: Commercial Airplanes - Cabin Air Quality Home is a good resource that is quite comprehensive. Bottom-line, the air in a modern jetliner is fresh (enough!) and, yes, the 787 will be better in this department, too.

Cheers:ok:

So indeed, with modern engines, the corporate penalty for clean cabin air is fuel consuption and power loss ( wrt Boeing article). The 50/50 mix is the norm but I'm sure this ratio can be 'confidentially' tweaked by company policy to reduce fuel burn.

Unless air quality is continuously monitored, to make it auditable, (quality parameters recorded along with other flight data) cabin air quality will continue to be poor in the interests of company operating costs.

Thread Hijack - Folk myth or truth.

I was told in the old days of "dirty" jet engines, that the dirty jet efflux was excess kerosene, and not soot. So far so good.

It was stated often that the kerosene trail left by jets in the upper atmosphere actually REDUCED the Ozone content of the atmosphere, but I am unsure of the reasoning, whether it be absorption, chemical combination, or whatever............

Then along came the lean and clean jets with much more efficient burner cans, leaving no kerosene trail, but actually contributed to Ozone levels.

Apologies for hijacking an Ozone thread, but I've always wondered, fact or fiction?

(Note that these stories originated in the 70's, when hardly a soul had any thought for environmental concerns. The jet pollution was considered "visual" pollution).

Regards,

Old Smokey

The humidity cue
 

If, as the popular myth has it, cabin air were endlessly recycled with negligible top up fraction from external air, on full flights it would rapidly become very humid, as the cabin is densely packed with paying living humidifiers. The portion of each exhaled breath that made it down to the alveoli has a very high dew point.

However, as is rather more generally and accurately known, the cabin air is actually very dry. So the top up from (extremely dry) external air is very substantial.

Funny that the 787 is mentioned here. I think the reference is backwards, as one 787 innovation is to _lower_ the fresh air input when the cabin has a small passenger load with a view to raising the cabin humidity a bit (mind you, still terrribly dry, at 14-15% rather than the single digits of earlier craft).

I think they should leave the kettles boiling in the galleys or fit humidifiers to increase humidity but not rely on exhaled air ... from peoples lungs
& legeionars disease.

Old Smokey
 

Is this some confusion with the relative NOx levels? Higher TET as achieved by modern engines leads to better fuel burn but also higher NOx levels, which cause O3 depletion.

I think....