Cabin Air Filtering

[bsmasher]

A ( hopefully) simple question for the experts out there

Whats the typical filtering regime on the recirculated air on 737s and 767s ?


Reason for the question, At the moment my partner has lowish white blood cells and is scared of picking up bugs especially airbourne ones from coughees in enclosed spaces - If I can show that there is good filtering in the cabin air systems it will go a way alleviate her fears of taking a short trip away.

Thanks in advance

[Ulster]

Hope this might be of interest :

The truth about cabin air (http://www.askthepilot.com/questionanswers/cabin-air-quality/)

[ExXB]

Many people claim they catch colds (etc) when travelling - but the aircraft cabin isn't the place they catch bugs. Travelling involves standing in numerous queues with the unwashed masses, and local transportation often in 'public' conveyances without any filtering (think about a taxi).

This is what Boeing (http://www.boeing.com/boeing/commercial/cabinair/index.page) has to say about air filtering on their aircraft. Note that the B737's first flight was in 1967 - unlikely you'd find one that old but systems will differ on the age of the aircraft. The B767 is newer - first commercial flight 1982.

You can avoid some of the queues, she doesn't have to stand with you while you check-in / drop bag or at the gate (wait until everyone else is on) but with security it's pretty well mandatory (although you could ask for assistance - and have your partner escorted through). Wash hands frequently too. Also use disposable masks (found at any pharmacy) but be careful - they lose their usefulness once touched, so she could need a few.

[BOAC]

The other tip (she probably knows) is to make sure she breathes through her nose as much as possible and not mouth. The inevitable nearby idiot sneezer/cougher you will encounter - that never learnt good manners - always prompts me to shield my mouth and ensure nasal breathing - 'Big G' built the nasal passages to filter bugs.:ok:

Good luck.

[bsmasher]

Thanks all for the helpful suggestions - I'd not really thought about the check-in bit - but now we'll look into things like doing it online to avoid queues

[OverRun]

Look, it is not the cabin air that is the problem. It is your own bugs being pushed around by varying cabin air pressure. What happens is that the air pressure in the plane varies throughout the flight. There is a sudden rise in pressure after the engines start, then as a flight climbs after takeoff the air pressure in the cabin decreases, and finally when the flight descends to land, the air pressure increases. As the engine power setting varies, pressure varies. On most planes, air is supplied to the environmental control system by being "bled" from a compressor stage of each gas turbine engine, upstream of the combustor. The temperature and pressure of this "bleed air" varies widely depending upon which compressor stage and the RPM of the engine.

Well, when the air pressure increases, it essentially forces the bugs trapped in your upper system (such as your nostrils and throat) down into your lungs and as it decreases, they get washed back up. Your lungs get washed again and again with bugs that the body would normally keep at bay. That’s what makes you sick.

The defence against all that is bolstering your immune system. The cabin air pressure is not the main culprit because it is the bugs you are carrying that nail you.

To bolster your immune system, there are a range of remedies down at your local pharmacy: Barley Green, Olive Leaf Extract, etc.
However a very effective one which is perfect for flying is the Chinese herbal mixture: Yin Chiao (Yin Chiao Chieh Tu Pien). Ugly brown pills, but they work. Chinese medicine shops will have it, or can buy it direct from here:
Yin Chiao (Yin Chiao Chieh Tu Pien), 96 ct, Plum Flower | 739934860397 | by Plum Flower (http://www.chineseherbsdirect.com/yin-chiao-yin-chiao-chieh-tu-pien-96-ct-plum-flower-p-38.html)

Before I got introduced to this by my Chinese doctor, we would fly from Australia to Europe and always at least one of us was sick by the time we landed. It got so that I pIanned the trip with the first week being sacrificial to cater for the sick person. But now no more. We are taking Yin Chaio (4 pills – lasting about 12 hours or so, so on a 24 hour trip, take it before takeoff and then again at the stopover). If you are on a short flight like USA-UK or UK-Europe, then only one lot of 4 is needed before takeoff. We haven’t got sick on a plane for the last 8 years except where someone forgets to take the pills.

[Mark in CA]

The majority of modern, large, commercial aircraft, which use a recirculation type of cabin air system, utilize fine HEPA filtration, (99.99% minimum sodium flame efficiency/99.97& minimum DOP efficiency).
Cabin Air Q&A (http://www.pall.com/main/aerospace-defense-marine/literature-library-details.page?id=46181)

[Agaricus bisporus]

Look, it is not the cabin air that is the problem. It is your own bugs being pushed around by varying cabin air pressure. What happens is that the air pressure in the plane varies throughout the flight. There is a sudden rise in pressure after the engines start, then as a flight climbs after takeoff the air pressure in the cabin decreases, and finally when the flight descends to land, the air pressure increases. As the engine power setting varies, pressure varies. On most planes, air is supplied to the environmental control system by being "bled" from a compressor stage of each gas turbine engine, upstream of the combustor. The temperature and pressure of this "bleed air" varies widely depending upon which compressor stage and the RPM of the engine.

Well, when the air pressure increases, it essentially forces the bugs trapped in your upper system (such as your nostrils and throat) down into your lungs and as it decreases, they get washed back up. Your lungs get washed again and again with bugs that the body would normally keep at bay. That’s what makes you sick.

The defence against all that is bolstering your immune system. The cabin air pressure is not the main culprit because it is the bugs you are carrying that nail you.

To bolster your immune system, there are a range of remedies down at your local pharmacy: Barley Green, Olive Leaf Extract, etc.
However a very effective one which is perfect for flying is the Chinese herbal mixture: Yin Chiao (Yin Chiao Chieh Tu Pien). Ugly brown pills, but they work. Chinese medicine shops will have it, or can buy it direct from here:
Yin Chiao (Yin Chiao Chieh Tu Pien), 96 ct, Plum Flower | 739934860397 | by Plum Flower

Before I got introduced to this by my Chinese doctor, we would fly from Australia to Europe and always at least one of us was sick by the time we landed. It got so that I pIanned the trip with the first week being sacrificial to cater for the sick person. But now no more. We are taking Yin Chaio (4 pills – lasting about 12 hours or so, so on a 24 hour trip, take it before takeoff and then again at the stopover). If you are on a short flight like USA-UK or UK-Europe, then only one lot of 4 is needed before takeoff. We haven’t got sick on a plane for the last 8 years except where someone forgets to take the pills.

Seldom, if ever, has such baseless and scientifically bankrupt twaddle ever been peddled on this forum, and that really is saying something.

Complete, total and utter crap from beginning to end, both the description of pressurization systems which bears no resemblance to reality whatsoever (though it might be the sort of hokum a chined=se doctor might invent) to the bullshine about pressure changes forcing bugs into your lungs.

Overrun, that post in nothing less than delusional and calculated to mislead.

I don't know what colour the sky is on your planet but remember this is a Professional Pilot's forum, not chemtrails or a witchcraft group, please don't waste out time here.

[Pinkman]

Actually Overrun isnt far off. Its not the dynamic effects of the pressure changes its your response in clearing the blocked eustachian tubes etc and all the grunting and snorting that goes with it that forces virus laden particles back down the bronchus and oesophagus when you perform the valsalva maneuver to equalize.

We all incubate Rhinoviruses in our noses that is why First Defence works (and is proven by peer reviewed science to work).

Yes the air is filtered - have you ever seen a Pall aircraft filter being changed? I have... its disgusting. Yuk.

Suggestions to help the OP:

1) Fly Business Class. Although the air refresh rate is probably similar per cabin volume, per pax it is proportionately higher and the concentration of unwashed people lower.

2) Use a saline rinse or First Defense before you leave home

3) Get a pack of decent N95 grade masks and USE THEM. 3M 1860 or similar. Use the aluminium pinch strip to ensure they fit. Remember they deteriorate due to breath moisture after several hours so change them regularly. Dont worry about people staring at you - if you were in Asia they wouldnt give it a second thought: the Japanese wear them in public places all the time. Put it on BEFORE you enter the airport.

4) Wash you hands regularly and take alcohol gel in a small 100ml bottle. Try not to rub your eyes or other mucous membranes unless you have used it (and it has evaporated!).

5) Boost your immune system. If you have a low WBC count you will know how.

Good Luck

[OverRun]

Ah thank you Pinkman for a more medical scientific explanation. I stand corrected on the source of the pressure moving the "virus laden particles back down", and apologise to the ECS designers I have offended.

The air pressure in the cabin varies throughout the flight though. From Kelly at al (reference below):

It is a commonly held belief that cabin air pressure is maintained at a constant level during long-haul commercial flights. A recent British Medical Journal editorial included the statement that cabin pressure is maintained at the equivalent of 8000 ft (2440 m) in altitude. As demonstrated in this study, cabin air pressure is not constant and decreases as aircraft cruise at higher altitudes in the latter part of long sectors.

Their figure 1 below is their measurement of the variation of cabin air pressure during one flight shows the scope for "grunting and snorting" responses:

http://profemery.info/cabin.jpg

This is not a criticism of the aircraft engineering, and it is important to note that even when at their highest cruising altitudes, the Boeing 747–400 aircraft studied provided cabin air pressure conditions that comfortably exceeded the current regulatory standards.

Their figure 2 is a summary of the relationship between aircraft altitude and cabin conditions taken from 45 flights, and shows that the magnitude of the pressure changes:

http://profemery.info/cabin2.jpg

REF: Directly measured cabin pressure conditions during Boeing 747–400
commercial aircraft flights. Paul T. KELLY, Leigh M. SECCOMBE, Peter G. ROGERS AND Matthew J. PETERS. Respirology (2007) 12, 511–515

[TightSlot]

I'm curious... I have worked as an FA for nearly 35 years.
...we would fly from Australia to Europe and always at least one of us was sick by the time we landed...
Why doesn't this happen to me, and indeed the rest of my crew?

[Pinkman]

Why doesn't this happen to me, and indeed the rest of my crew?

I don't know, but the science says that you are an exception.

The Chartered Institute of Environmental Health released a study in 2004 titled "Common cold transmission in commercial aircraft: Industry and passenger implications"

The Chartered Institute of Environmental Health - JEHR - Common cold transmission in commercial aircraft: Industry and passenger implications (http://www.cieh.org/jehr/jehr3.aspx?id=11412)

Reading the study I am wondering if stress and fatigue are greater contributors than we realize. If you have been doing this for 35 years you obviously enjoy it and will find it less stressful - god forbid even enjoyable - than even the most frequent pax (like me sadly). That would explain the fact that as a cohort cc have anecdotally fewer colds than pax.

[TightSlot]

There are quite a few of us that are exceptions then? :)

Please forgive my scepticism, but I'm just not buying what is being offered. I simply don't accept that aircraft cabin air and environment are inherently any more "risky" than any other environment where human beings cluster together - in fact, it might be argued that there is a lower risk due to the filtering process. To change my view on this would require something more concrete than a Chinese Doctor and some anecdotal "evidence".

[OverRun]

Tightslot, there are at least three possible reasons for CC not getting ill very often.

The first is that there is a lot of engineering in the commercial jet airliner environmental control system (ECS) to stop the bugs from being circulated. Mark in CA mentioned this. From Leder and Newman (reference at the bottom):

Although concern has been raised about air quality and spread of respiratory pathogens on aircraft, studies of ventilation systems and patient outcomes have suggested the dissemination of pathogens occurs rarely. This is because outside air entering the cabin at altitude is essentially sterile, heating/cooling further reduces microbial risks, HEPA filters remove microorganisms from recirculated air and the low humidity, high airflow rates, laminar airflow pattern and frequent air exchanges incorporated into the cabin ventilation and pressurization systems further minimize microbial contamination on board aircraft.

Secondly, the air circulation area within the cabin is limited. There is a common misconception amongst the travelling public is that if one person on board an aircraft has an infection, then all other passengers are at risk. Because air flow is generally from top of the cabin to the bottom, with little if any front to back flow, and because respiratory pathogens are diluted by frequent air exchanges, passengers at most risk are those in close proximity to the infected passenger, with minimal risk for others. So CC moving around the cabin are only in close proximity with a sick passenger for short periods at a time.

Op.cit. The air enters the distribution pipework for delivery to the cabin. Cabin air is taken from below the floor of the aircraft to the overhead cabin ventilation system, which runs the length of the cabin. The ventilation system is usually designed so that air entering the cabin at a given seat row is exhausted at the same seat row. This limits the amount of air flowing in the fore and aft directions (i.e. towards the front and back of the aircraft, respectively), which also helps minimize infection risk.

Pinkman quoted the JEHR paper, and this supports both those points: it mentions that in that a passenger survey conducted by Zitter and coworkers suggests that cabin air recirculation has little impact on the incidence of colds.

The third reason could be differences between CC and passengers:
- is it possible that CC are less likely to go to work with upper respiratory tract infections whereas passengers might still travel even if they are slightly unwell,
- differences in stress and fatigue differences as Pinkman is suggesting,
- and/or for those of you that have read Pinkman's link to the JEHR paper on "Common cold transmission in commercial aircraft: Industry and passenger implications", it raises the real possibility that CC have developed an ability to resist infection while flying - specifically because CC developed improved resistance to the effect of exposure to dry air reducing the nasal mucociliary clearance. I have the two papers by Salah et al, and by Barry et. al. which are in the references to the JEHR paper. The Salah paper notes that there are "large inter-individual variations of the saccharin nasal transit time in our subjects, an observation already reported [21, 22], but the reasons for such large differences are still unknown." Basically some people are more affected by dry air, and their nasal mucociliary clearance system is reduced or stopped and that increases susceptibility to colds. Others are less affected, and I am wondering if this is a response learned over time and exposure by CC.

If you haven't read the JIEH paper, then let me extract a bit for you:
The natural human defence system against colds is known as the Mucociliary Clearance System, which consists of a layer of thin mucus that is kept in motion by beating cilia. This protective system traps viruses and bacteria and moves them from the nose and throat to destruction by acids in the stomach. However, when the air is dry, the mucus becomes too thick to be effectively moved by the cilia. This leaves more viruses and bacteria to cause upper respiratory tract infections. The typical relative humidity in aircraft cabins for flights over an hour is below 10% for most of the journey, often dropping to less than 5% on longer flights. It has been shown experimentally, using saccharin, that under these conditions the Mucociliary Clearance System either slows dramatically or stops (Barry et al, 1997, Salah et al, 1988). This would suggest that it is the low relative humidity in aircraft cabins that increases susceptibility to colds rather than a higher viral load in the air.

I guess after all this I can re-write my earliest post and say:

Look, it is not bugs in the cabin air that is the problem. Studies of airplane ventilation systems and patient outcomes have suggested the dissemination of pathogens occurs rarely. However the dry cabin air reduces the natural human defence system against colds, and your Mucociliary Clearance System either slows dramatically or stops. Fatigue and stress play a role. When you respond to pressure changes in the cabin by clearing the blocked eustachian tubes etc and all the grunting and snorting that goes with it, that forces virus laden particles back down the bronchus and oesophagus when you perform the valsalva maneuver to equalize. Looking at the graph of cabin pressure vs altitude, I think the problem time is on descent after hours of flying in very dry air. It is your own bugs being pushed around by varying cabin air pressure. Your defences against that have been given by Pinkman. And there are various ways of boosting the immune system.


REF: K. LEDER and D. NEWMAN Respiratory infections during air travel. Internal Medicine Journal 2005; 35: pp50–55.

[darkroomsource]

I simply don't accept that aircraft cabin air and environment are inherently any more "risky" than any other environment where human beings cluster together

Exactly.

On long flights, though, we tend to find ourselves in an area with more people per cubic metre (or cubic foot if you want to think in feet) than we find ourselves in the majority of our daily lives. Thus, when on long flights, we are more susceptible to germs, not because the air isn't filtered or is filtered, but because there are more of us in a smaller space. Even if the air is not filtered, but entirely fresh on every cycle through the plane, it has to come in somewhere and go out somewhere, and in between it goes past people.

I flew from Panama to the US a few years back, and there was a carry-on filled with mothballs in the overhead. When the flight crew opened the bag (because of the smell), the two of them fell to the floor immediately, several passengers passed out, the copilot got "dizzy" and the pilot put on oxygen and we did a "precautionary" landing in Mexico.

If the bag had been opened outside, and we were all gathered around in the open air, I doubt anyone would have been affected.

It's all about confined space, and an individual's ability to fend of germs. And as has been written already, there are ways to reduce your chances of being affected by other people's germs, follow safe practices and you're less likely to be affected.

I haven't generally been affected on flights, but my son, who suffers from asthma always used to get some kind of bug on long flights. We started taking precautionary measures with him (bathing before and after the flight, hand gel, masks, etc.) and he was no longer affected.

[ExXB]

Yes, flying involves being crowded together much more densely than we normally are in our day-to-day lives. The good news is that the HEPA filters do a very good job of screening out viruses while we are on the aircraft. However airports with their endless queues do nothing equivalent.

You are much more likely to pick up a virus while travelling, from the moment you hope into that taxi, to the moment you hop off that hotel shuttle bus. But the aircraft is at the bottom of the list of where you may have picked up that bug.

When travelling wash your hands frequently, whip down your tray with an alcohol based towelettes. Avoid queues, to the extent possible, and avoid touching things. If you've already got a cold, where a mask. You may avoid spreading your germs to the next guy.

[Pinkman]

I simply don't accept that aircraft cabin air and environment are inherently any more "risky" than any other environment where human beings cluster together

As Nicolas Cage said in City of Angels ... "Just because you don't believe it, doesn't mean it isn't true"

The fact is, and you can argue this all you want but it it is demonstrable that cabin air is, for the most part, acceptable for the majority of people - including cc - for the time that they typically spend on aircraft. It is also demonstrable that cabin air is not the same as an equivalent ground-level setting where people are clustered together eg a cinema

1) It is not delivered at the same Barometric Pressure or Relative Humidity

2) It is usually recycled with a smaller proportion of make-up air (some industrial systems for buildings do this also... as in sick building syndrome)

3) There MAY be contaminants - such as oil mist and Tri Cresyl Phosphate inadvertently introduced into the bleed air and which in the latter case is a known neurotoxin. Some aircraft are suspected to be worse than others (anecdotally the 757 and 146/RJ) and some people including pilots & cc - have allegedly been found to be hypersensitive to very low levels of TCP whereas most of us are unaffected.

4) The very basic fact that people tend to travel even if they are sick because typically travel isn't discretionary, but the same people tend not to go to the cinema if they are feeling unwell. When did you last hear of someone getting TB from a coughing neighbor in the cinema? There are loads of instances every year where this happens on aircraft.

So whereas I agree that for the majority of people cabin air is acceptably safe, I don't accept that there is no difference between being in a crowded place for 12 hours or on an airplane for 12 hours. And I say that having spent a good proportion of my life as an Occupational Health Professional when I wasn't analyzing Jet fuel in the lab. When I was 11 years old I was involved in a oil fume incident in a VC-10 (G-ARVI) in Dharan, and I honestly thought I was going to die, I was so sick. A small washer had deteriorated (the FE showed it to me) and allowed oil mist to enter the cabin. Thanks to the promptness of the BOAC cc we were all bundled off (it was a schoolkid special) and made comfortable but since then I have read avidly on the subject. It influenced my career choice.

[ExXB]

There are loads of instances every year where this happens on aircraft.

Could you kindly give us some references to support this. I tried googling it and found a few references to 4 passengers catching TB on a US Air flight, in 1995.

This is what the CDC (http://www.cdc.gov/tb/publications/factsheets/general/tbtravelinfo.htm) says about it:

Are international travelers at risk of getting drug-resistant TB while traveling?

Although MDR and XDR TB are occurring globally, they are still rare. HIV-infected travelers are at greatest risk if they come in contact with a person with MDR or XDR TB. All travelers should avoid high risk settings where there are no infection control measures in place.

Documented places where transmission has occurred include crowded hospitals, prisons, homeless shelters, and other settings where susceptible persons come in contact with persons with TB disease.

Air travel itself carries a relatively low risk of infection with TB of any kind.

Thank you.

[Pinkman]

Its a fair question. I've researched it, written about it, and looked at the references (and looked at the new ones in response to your question).

In 2006, in a document I edited for our industry

Managing tuberculosis | IPIECA (http://www.ipieca.org/publication/managing-tuberculosis)

I said "According to the WHO, the risk of acquiring TB infection during air travel is similar to that associated with other activities in which contact with potentially infectious individuals may occur (e.g. train travel, bus travel, any gathering in enclosed spaces). Only passengers in the same section of the aircraft appear to be at risk. This risk is minimal in flights under eight hours duration". That was the 2006 guidance from WHO and I had visited them in Geneva to discuss this.

But although that guidance hasn't much changed I am no longer convinced this holds especially on longer flights. Think about it: nearly two billion passengers fly annually. One third of the worlds population is infected with TB (granted not all of those are infectious or have active or MDR TB).

We've drifted off the OP's request which was on cabin air: I am not suggesting that cabin air that is properly filtered through regularly changed HEPA filters isnt safe. I am not suggesting that circulation of air has any more than an incidental role as a carrier of infectious droplets. But the extended flights we do now are very different from 90 minutes in a cinema. We've had cases on offshore rigs with shared accommodation where two HIV infected trainees from Africa (who were tested negative for TB because of immunosuppression) infected many co-workers in their two week rotation.

I am getting you the references and will re-post tonight.

[OverRun]

While Pinkman gathers his references, I looked again at the HEPA filters. What we have discussed above is that the use of appropriate filters and correct recirculation of air in the plane reduces the risk of infection. Although the safety of HEPA filters in protection against viruses has been questioned, (Gammaitoni I, Nucci MC. Using a mathematical model to evaluate the efficacy of TB control measures. Emerg Infect Dis. 1997;3: 335-42), a more serious concern is the absence of legislation obliging their use in most countries.

HEPA filters were found not to be used on 15% of flights carrying more than 100 passengers in the USA, and that figure is considerably higher in small planes that undertake local flights (United States General Accounting Office. Aviation safety: more research needed on the effects of air quality on airliner cabin occupants. [Cited 2005 Sept 26] January 2004, Washington, DC. Available from: http://www.gao.gov/new.items/d0454.pdf). I just downloaded this, and the actual paragraph is:

Several technologies are available today that could improve cabin air quality, (e.g., increasing cabin humidity and pressure or absorbing more cabin odors and gasses); however, opinions vary on whether FAA should require aircraft manufacturers and airlines to use these technologies. GAO found that one available technology, high-efficiency particulate air (HEPA) filtering, was strongly endorsed by cabin air quality and health experts as the best way to protect cabin occupants' health from viruses and bacteria in recirculated cabin air. While FAA does not require the use of these filters, GAO’s survey of major U.S. air carriers found that 85 percent of large commercial airliners in their fleets that recirculate cabin air and carry more than 100 passengers already use these filters. However, the use of HEPA filters in smaller commercial aircraft that carry fewer than 100 passengers is much lower. The cost to retrofit the smaller aircraft to accept the HEPA filter, if it were made mandatory, could be expensive.

OK, the smaller (<100 pax) planes are not likely to be doing extended flights, but that still leaves the 15% to think about.

I wonder if this figure is reflecting the USA fleet composition in 2004, and now in 2013, planes with air recirculation and without HEPA filters have been retired?

And I wonder what it means elsewhere in the world? In Asia/Europe/Australasia, I would guess that the advent of LCCs with fleets of sparkling new 737NGs and A32x aircraft has meant that almost all aircraft >100 pax have HEPA filters, but that is only a guess and is open to someone more knowledgeable to comment.

[Pinkman]

Air Travel and TB: An airline perspective
Nigel P. Dowdall, Anthony D. Evans, Claude Thibeault
Travel Medicine and Infectious Disease (2010) 8, 96e103

Guidance from WHO on the prevention and control of TB during air travel
Lindsay Martinez, Kathrin Thomas, Jose Figueroa
Travel Medicine and Infectious Disease (2010) 8, 84e89

Transmission of infectious diseases during commercial air travel
Alexandra Mangili, Mark A Gendreau
Lancet 2005; 365: 989–96

Transmission of multidrug-resistant Mycobacterium tuberculosis during a long airplane flight
Kenyon, Thomas A, Valway, Sarah E, Ihle, Walter W, Onorato, Ida M, Castro, Kenneth G,
The New England Journal of Medicine 334.15 (Apr 11, 1996): 933-938.

http://www.gcaqe.org/documents/FAAmedicalprotocol.pdf

[ExXB]

This thread has involved well beyond the ken of this SLF. While interesting, it may get more informed responses in the Tech forum.

[bsmasher]

In the end it all worked out. A big thank you needs to go to the security team at Sydney T2 last Friday. Due to work pulling me to Melbourne earlier in the day for a meeting my partner had to make the trip by herself. She was feeling a bit overwelmed by the whole experience and left her bag at the security check. When she got back there the team there gave it back and went well out of thier way to to a fine job of being calming and supportive to an anxious passenger and getting her back to the gate on time. A positive to security for once!!!

A good weekend away ( helped by the info from the pprunites) to help in recovery from the effects of too much hospital time recently. Thanks all!

[Chocks Away]

It is in the Tech Forum also but here's the latest on the clean Cabin Air debate. (http://www.breakingtravelnews.com/focus/article/only-the-boeing-787-provides-passengers-and-crews-with-clean-breathing-air/)