cabin air quality

[riverfish]

Hello.
I wonder if I may trouble you for a technical opinion.
I am a gp, and a patient of mine has Lymphoma (a cancer of the lymphatic system) They have received chemotherapy, and thishas worked well, and they are now in remission.
The chemo will have thrashed their immune system, so they will not have quite the same ability to fight off infection as a person who has not received such poison.
They are allowed to do what they like in terms of going to public places, concerts etc, but have had the fear of god put into them with a total ban on flying as they may catch something from the filthy and germ ridden air that is in airoplane cabins.
It was my understanding that this is air is replaced by air that is sucked in through the engine(hence the problems that have been caused with leaky seals and oil.)
Presumably recirculated air goes through some sort of purification/filtering system....I would have thought that breathing unacceptably contaminated air would be not acceptable.
It sounds like an urban myth, concocted by those that dont understand, but think they do.
She overheard some other lad in the clinic have a hell of a bollocking, as they found that he had just returned from skiing!!!!


Any thought or advice welcome.....If you want advice on your ingrowing toenail, I can return the favour!!!!!!

[doncas]

To hopefully answer your question,
First of all, the air that is in the cabin isn't filty or germ ridden as you have inferred.
Air is indeed drawn from the engines, but nowhere near the combustion end of the engine. It is drawn from the compressor section. It is then brought from here to an air conditioning pack(air conditioning unit). The air is cooled at this point by an air cycle machine, (by means of volume expansion) and in then put in to an air mix manifold.

At this point, some cabin air, up to 20% is mixed with the freshly introduced air, and circulated in the cabin via riser ducts. The air then mostly escapes to the atmosphere, and some is brought back to the air mix manifold.

Ultimately, you will have a full cabin air replacement every few minutes, depending on the size of the aircraft.
During this process, the air is passed through a HEPA filter that is regularly replaced.

With regard to your concern on contamination of the cabin air from engine oils etc, as the air is drawn from the compressor stages of the engines, there is very little cbance of engine oil or hydrocarbons being introduced. The air is passed through several stages that would cause any contamination, no matter how small to be prevented from reaching the mix manifold.

If you want some more specific information on any of these stages, please ask the question,

Cheers

D

[shinobi1]

Further to Doncas concise reply, here are a couple of links that tell it from the horses mouth.

Boeing: Commercial Airplanes - Cabin Air Quality Home (http://www.boeing.com/commercial/cabinair/index.html)

http://www.scientificjournals.com/sj/espr/Pdf/aId/2518

There are many more links available on Google, including many scare-monger sites! But as a doctor, I'm sure you are well praciced at sorting wheat from chaff!

Shinobi