aircraft ventilation

[ludwig]

How does fresh air get into a passenger aircraft. Or doesn't it?

[ludwig]

Specifically, I'm wondering where all the fart gasses go on a long haul flight. Sorry to be so blunt, but we need to know these things.

[Clanad]

Depending on the make and model of aircraft, it has within it, usually in the far aft (rear, behind a pressurization bulkhead)) of the aircraft a device called an air cycle machine. Essentially it is a turbine powered by bleed air, which is compressed air pulled out of the jet engines before fuel is introduced. That hot air is run through the machine, cooled and controlled as required by thermostats set by the crew and vented into the cabin along the lower sides. This is supplemented by fresh air taken into the aircraft through vents, usually in the vertical tail section and passed into the aircraft through the "eyeball" vents over your head. This is all, then exhausted out of the aircraft through the pressurization controllers. The air is exchanged several times per minute...

[ludwig]

Thanks clanad, that's one less thing I have to worry about.

[alfiebrady]

I thought that, since the prohibition of smoking on airlines, the operators had introduced the practice of simply recycling the air instead of refreshing it - saving themselves a huge amount in fuel costs...?

[Clanad]

The Federal Aviation Administration (FAA) publishes rules applicable to the certification of aircraft when they are first proposed for manufacture. This is true of other countries that manufacture these types of passenger carrying aircraft. FAR No. 25.831 states that an airliner's ventilation system must be designed to provide each occupant with at least 0.55 pounds of fresh air per minute. That translates to about 10 cubic feet of air a minute. There really is no way to limit the "fresh air" intake since it is tied directly to the pressurization process for the aircraft. The pressurization acts like a balloon... letting in so much air and letting out so much air to maintain a desired ratio dependant on altitude of the aircraft. A lot of what you read is misinformed gibberish and included in books and news articles to alarm passengers and sell books... in my opinion...

[alfiebrady]

Clanad, what do you reckon to this (seriously)?

http://www.flyana.com/index.html

http://abcnews.go.com/2020/Health/story?id=1213901&page=1

The first seems to fall into your book-selling, alarmist gibberer category, but the second, while dispelling the myth of infection, suggests that some planes do recycle instead of replenish.

(ludwig, sorry if this is hijacking your q)

[jaydj]

I heard the same as alfiebrady that the airplane re-uses the old air now that smoking is banned

It is thought this is why there is more "flight rage" as passenger get stale air and makes them more grumpy

[Clanad]

Ms. Fairechild was specifically one of the authors I had in mind... Fact is (I have been an Airline Transpot Pilot for more years than I can remember) it is the heighth of uniformedness to state that pilots get more oxygen than passengers. They have exactly the same air source as do the passengers. They do have the availability of oxygen masks, but they are never used with the exception of flight above 35,000 feet if one of them has to leave the co0ckpit to use the lavatory, which is a matter of regulations. I'm amazed that someone hasn't called her on it except that the myths she expounds are so rampant from so many sources that no one in the industry bothers...The ABC source (I could only find the one page) is accurate in that any group of people forced to sit in proximity to one another for extended periods of time are probably going to experience higher rates of virus infections, such as colds. Ask any grade school teacher...
Thanks for the input, by the way...

[markja]

why don't they just open a window? doh!

[brachiopod]

Don't be stupid, markja, you can't just open a window in an aircraft......

....you'd let all the cold in and there'd be an awful draught. Besides, they are all fitted with those window locks to stop burglars from breaking in.....