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Sasha
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Cabin Air System As Infection Transport?

Mon Aug 25, 2008 11:58 pm

Hello,

I'd like to address these question to those in MX or with general knowledge about air flow systems on airplanes.

The background story is this: Today on our local newswire appeared an article about an "unknown" type of infection hitting our town of 300 000. Doctors indicate the sympthoms similar to that of the flu : high body temperature, headache, feeling cold, with a difference that it affects lungs, causing heavy caugh, resulting in severe breathing difficulty.

There's a suspicion that it may have smth to do with ... an airplane. The thing is that the town in question is YKS (UEEE) and is very remote from the rest of the world - no railroads, flights are limited coz the costs are prohibiting, vehicle roads are in condition beyond comfortable and even safe travel (as pictured in Ewan McGregor's The Lond Way Round documentary). Still most people travel for vacation to the rest of Russia and abroad, by air. Our local carrier just for over a year has been operating two Boeing 757-200 (ex-Icelandair, AFAIK). Passengers reportedly noted that the air in the cabin was "unpleasant to breathe after around 30 mins into the flight" and all reported disembarking the plane after flight caughing. A family is known to have been ill for a week after the flight. It sure may be speculation or genuine coincedence.

Anyway, how do air ventilation systems work on such aircraft? Are there any anti-bacteria or anti-viral means or does the air not circulate but constantly injested from the engines ( in which case not much of an issue...). However if the air flow is closed circuit then surely one infected passenger could indeed be spreading the virus during a 6 hour or longer flight to the rest of the cabin...
Thanks for any thoughts.

[Edited 2008-08-25 17:01:26]
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pilotpip
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RE: Cabin Air System As Infection Transport?

Tue Aug 26, 2008 1:38 am

Aircraft use air taken from the engines' compressors, the air is passed over exchangers to cool it and then it comes into the cabin. The air is constantly circulated by the natural flow created by the lower pressure outside the cabin and recirculation fans.

Airflow isn't closed circuit. While some of the airflow is recirculated, it is filtered. The air coming from the engines is already sterile due to the high temperatures as a result of being compressed. There is a certification standard that the cabin must also be able to quickly evacuate smoke and this is often accomplished by having fresh air come through.

In a small, remote town like yours the likelyhood of everybody getting sick due to daily interactions is much more likely than from an airplane.
DMI
 
tdscanuck
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RE: Cabin Air System As Infection Transport?

Tue Aug 26, 2008 2:29 am



Quoting SashA (Thread starter):
Anyway, how do air ventilation systems work on such aircraft?

As PIlotpip described.

Quoting SashA (Thread starter):
Are there any anti-bacteria or anti-viral means or does the air not circulate but constantly injested from the engines

There's a fairly good filter in line.

Quoting SashA (Thread starter):
However if the air flow is closed circuit then surely one infected passenger could indeed be spreading the virus during a 6 hour or longer flight to the rest of the cabin...

It's not fully closed circuit. It is partially recirculated (otherwise the relative humidity would be near 0% and you'd feel *horrible*). However, the air change over rate is *far* higher than it is in any residential or commercial building, so you're getting a much larger amount of fresh air when you're on an airplane than almost anywhere except standing outside.

Quoting Pilotpip (Reply 1):
In a small, remote town like yours the likelyhood of everybody getting sick due to daily interactions is much more likely than from an airplane.

It's also possible that someone brought in something from afar that nobody in the town had been exposed to before...in that sense, airplanes are major factors in disease spread because they allow germs to travel long distances very quickly, but that's not the fault of the aircraft air system.

Tom.
 
BE77
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RE: Cabin Air System As Infection Transport?

Tue Aug 26, 2008 3:41 am

They could be running the cabin pressure a little lower than they should (which would save some small but significant amonunt of fuel at $115 oil). That would result in drier air, which doesn't do your throat a lot of good. An altimeter watch if you have or can borrow one will show this pretty quickly (or a barometer, but security might look at you with suspicion!)

There is also the air filter system - usually pretty good (hepa, etc.), but like anything, if they are not look after, then instead of an air filter system, you might have a germ distribution centre.



Quoting Tdscanuck (Reply 2):
t's also possible that someone brought in something from afar that nobody in the town had been exposed to before

I find that after a long working trip and the flight to and fro, I end up with a flu or cold 3 days later about 1/4 of the time. Discussion with medical friends pretty much agrees on it being exposed to all sorts of weird and wonderful things that we haven't had at home yet (funny, but when I get back from a trip, they always ask if I have a flu before agreeing to meet!)
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411A
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RE: Cabin Air System As Infection Transport?

Tue Aug 26, 2008 5:10 am

As all three of us on the FD occasionally smoke Havanas, the air exchange on the L1011 (once every three minutes, ,approximately) is put to very good use.
Normally, electrically opening the forward outflow valve slightly more than the aft outflow valve aids in FD ventilation.
 
SlamClick
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RE: Cabin Air System As Infection Transport?

Wed Aug 27, 2008 3:36 am

IF cabin crew do have higher than normal incidence of respiratory problems I doubt that the culprit is the cabin air itself. (Except that it tends to be quite dry - the humidity coming mostly from people exhaling)

It is so easy to spread things like that through indirect contact like
> sneeze
> wipe nose with hand
> touch door knob

and relatively difficult to spread it through the air itself.

Quoting BE77 (Reply 3):
They could be running the cabin pressure a little lower than they should (which would save some small but significant amonunt of fuel

To my knowledge nobody runs the pressure lower for that purpose. Cabin altitudes are often around 8000 feet and at ten thousand they'd have to put everyone on oxygen. What is done is to run the air FLOW RATE lower.

Quoting Tdscanuck (Reply 2):
It's also possible that someone brought in something from afar that nobody in the town had been exposed to before...

Seems likely to me - a la "War of the Worlds. No immunity. Cities, especially dirty cities seem to promote thermonuclear immune systems.
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Starlionblue
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RE: Cabin Air System As Infection Transport?

Wed Aug 27, 2008 4:28 am



Quoting SlamClick (Reply 5):
It is so easy to spread things like that through indirect contact like
> sneeze
> wipe nose with hand
> touch door knob

That's why I was taught to sneeze into the back of the forearm instead of the hand, and wipe with the same place, or a tissue. Unfortunately there is a lot of sneeze, shake hand a bit, doorknob as you say.

Quoting SlamClick (Reply 5):
Cities, especially dirty cities seem to promote thermonuclear immune systems.

So true. During the first few months after we moved to HK, the kids seemed almost constantly sick. That tapered off after 3-4 months, with a blip when #1 started pre-school. But nowadays they're almost never sick.


Low humidity does not make you sick in itself, but it can tend to irritate airways, making them more susceptible to infection and slowing the healing process.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
pilotpip
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RE: Cabin Air System As Infection Transport?

Wed Aug 27, 2008 5:14 am



Quoting SlamClick (Reply 5):
IF cabin crew do have higher than normal incidence of respiratory problems I doubt that the culprit is the cabin air itself. (Except that it tends to be quite dry - the humidity coming mostly from people exhaling)

It is so easy to spread things like that through indirect contact like
> sneeze
> wipe nose with hand
> touch door knob

and relatively difficult to spread it through the air itself.

I get a kick out of the captains that constantly use anti-bacterial wipes nonstop. I'll do it as part of my first flight flow, mainly because of how dirty things are. Most of the time I take one for pre and postflighting the lav as well  Smile Suprisingly, the ones that use them most and are constantly in the Germ-X seem to be the ones that are sick most often.
DMI
 
SlamClick
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RE: Cabin Air System As Infection Transport?

Wed Aug 27, 2008 5:56 am



Quoting Pilotpip (Reply 7):
Suprisingly, the ones that use them most and are constantly in the Germ-X seem to be the ones that are sick most often.

That was my observation as well, but I'm of a skeptical nature since Adelle Davis, the health guru of my generation died of [in her own opinion] malnutrition. I think Euell Gibbons died of elm blight at about the same time but I'm not sure about that.

I don't know much about how it works but I think the immune system needs current models to build its defenes against. No point looking for WMDs where they ain't, so to speak.
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Starlionblue
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RE: Cabin Air System As Infection Transport?

Wed Aug 27, 2008 6:02 am



Quoting Pilotpip (Reply 7):
Suprisingly, the ones that use them most and are constantly in the Germ-X seem to be the ones that are sick most often.

You said it!

Quoting SlamClick (Reply 8):

I don't know much about how it works but I think the immune system needs current models to build its defenes against. No point looking for WMDs where they ain't, so to speak.

Many many doctors feel that the current generation of parents is keeping kids too clean. Said kids end up with more allergies, asthma and general nastiness than their predecessors.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
BAE146QT
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RE: Cabin Air System As Infection Transport?

Wed Aug 27, 2008 4:59 pm



Quoting Starlionblue (Reply 9):

Many many doctors feel that the current generation of parents is keeping kids too clean. Said kids end up with more allergies, asthma and general nastiness than their predecessors.

I believe this to be correct. Not quite the forum for it, but acquired immunity from the mother only lasts for around 6-12 months, and only includes things that she's immune to.

After that, only direct exposure to pathogens will stimulate B- or T-cell memory to provide continued active immunity. And the ability for those B- and T-cells to 'learn' diminishes with age. So unless you're allowed to roll in the mud as a kid, you really risk being a sickly adult.
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Sasha
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RE: Cabin Air System As Infection Transport?

Thu Aug 28, 2008 7:07 am

Thank you everyone for your input in clearing up the air around airflow issue  .

And I agree on the parents bringing up kids too "soft and sterile" these days. Parent myself and somehow meet strong opposition from fellow parents of similar age and own spouse who believe in the "green house" style parenting. I believe our kids should be brought up in a way not so different from what our parents did for us - afterall we're alive and reproductive aren't we - how wrong could they have been?   .

[Edited 2008-08-28 00:08:43]
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Starlionblue
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RE: Cabin Air System As Infection Transport?

Thu Aug 28, 2008 10:05 am



Quoting SashA (Reply 11):
I believe our kids should be brought up in a way not so different from what our parents did for us - afterall we're alive and reproductive aren't we - how wrong could they have been?

I believe it should be a mixture of old and new. Certainly infant mortality and expected lifespan figures keep improving, so something must be changing for the better.  Wink However I am with you that many parents seem convinced their children are made of glass.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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HAWK21M
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RE: Cabin Air System As Infection Transport?

Thu Aug 28, 2008 10:42 am



Quoting SashA (Reply 11):
And I agree on the parents bringing up kids too "soft and sterile" these days

Exposure to small infections will boost immunity due presence of Anti-bodies in due course.Too protective environment can be harmfull in the long run.
regds
MEL
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Sasha
Topic Author
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RE: Cabin Air System As Infection Transport?

Thu Aug 28, 2008 11:16 am



Quoting HAWK21M (Reply 13):
Exposure to small infections will boost immunity due presence of Anti-bodies in due course.Too protective environment can be harmfull in the long run.

Perhaps I didn't word that properly - yes I acknowledge there're such parents and I am against all that green house kid raising. I wasn't supporting their cause  Smile
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