Is in-cabin air circulation/re-circulation managed to maintain good health?

Been too busy since 15 may 2013 to get back on the forum as much as I would like.

I shall revert on this one as soon as time permits, and maybe all you younger engineers will see some light ahead in being pro-active and research oriented with the co-operation of airline/employers who recognise that much pioneering work begins in British ‘brains’.

There is a lot that can be done in the future by harnessing bio-technology to supplement the technical advances in civil aircraft.

Have to say I flew as cabin crew for nearly 6 years and didn’t feel I was any worse for it. In fact I get more infections now working in an office because the poor fragile things I work with get cold if you open a window for fresh air.

OK. To sum up, Cough’s and sneezes spread diseases?

I have no idea what you are getting at

Rgds Cking

Pics attached highlight a point made in my opening post

The two pics attached highlight a point made in my opening statement. The soot/dirt fell from the ventilation ducts completely on to a passenger in one incident and in the one I have taken a discrete pic of the soot also landed on the floor and on a pax’s trousers.

In my opening post in this thread I stated –

“Indirectly related albeit to LHR only is –

Interestingly the London Underground Piccadilly Line which carries many thousand LHR pax and staff a day has the poorest control of it’s on board carriage/compartment filters.

Twice I have seen with my own eyes black soot/dust fall in great lumps on to pax clothes from the overhead filters/ventilation units.”

I attach two pics of one of the two incidents I saw with my own eyes.

It particularly occurs during extra fast speeds that the Piccadilly Line Underground Trains get up to e.g. between LHR T5 and T1,2,3 stations.

If and when you are in any London underground stations look where possible along the track into the tunnels at either end of the platform. Also sometimes the train passes illuminated stretches of track and a glance through the windows will give you a sight similar to that described. The soot, dust and dirt are excessive.

This is the ‘filth’ inhaled by most pax including those travelling to and from LHR.

The problem is compounded if the pax from LHR are coming from aircraft “not so responsible” airlines that aren’t being maintained. These pax may have collectively become carriers of bacteria and viruses by being in an enclosed space (aircraft) with others who had illnesses or were already carriers.

On some long haul sectors on an aircraft, one has just to try to use the toilets and one reaslises how bad some pax hygiene and habits are.

I respect that the London Underground has been serving us well for 150 years BUT ……. shouldn’t passengers breathe as ‘clean air’ as possible now and in the future?

To complain to the authorities about London Underground will probably invoke a strike.

One advantage a pax on London Underground has is that they can chose alternative means of travel which isn’t possible with aircraft (once inside you are stuck inside until the next airport at least).

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Hi Paul F

I am the first to agree that there is NO 100% perfect system.

While most industries (airline, public transport, building [ventilation] including hospitals) improve technically they leave behind some ‘respect’ for transmission of illnesses by not always being pro active with regards ventilation, [e.g. why not consider developing self diagnosing filters ?].

In temperate climates enclosed spaces are made safe from the cold but aren’t always regulated correctly with respect to temperature and humidity and ventilation.

Just today the UK is reported as one of the few countries that has an open door attitude to the NHS being used/abused for free health care. See article in The Daily Telegraph Wed 15 May 2013 titled “Inadequate Insurance ? You may not make it past airport arrivals”.

Some airlines cut corners where they think they can get away with it.

Although I don’t have the technical knowledge to ascertain if some of these are suitable – certainly similar devices would allow LHR to introduce discrete checks

http://www.qasupplies.com/systemsureplus.html

http://www.hygiena.net/docs/SS3_brochure.pdf

http://www.naturalstandard.com/index-abstract.asp?create-abstract=genomichandheldnaanalyzer.asp&title=Handheld%20nucleic%20acid%20analyzer

http://www.rigakuraman.com/applications/#threat-screening

http://www.strathkelvin.com/waste_water/scope.asp

http://www.space.com/4002-handheld-microorganism-detector-tested-aboard-space-station.html

Reducing the drain on the NHS and reducing employee absence through illness caused by cross infection is not something to be ‘tossed aside’ without a second glance.

Hi Jay,

There are two different issues here, one is ensuring that any bleed air drawn off from the engine compressors (or other engine related source) is not contaminated with things like traces of engine/compressor lubricants, and two trying to ensure the air in the cabin is as free from microbial contaminants (viruses and other undesirable organisms as possible).

Each aspect needs it’s own controls and checks – for example checks on efficiency and integrity of relevant engine seals and heat exchanger cores will help prevent contamination with lubricant oils etc, checks on efficiency and integrity of things like HEPA particulate filters may help keep levels of airborne microbes down.

I am not an aviation engineer, but I work in another tightly regulated industry (pharma/food production) where contamination of the end product is a similar concern, and all relevant steps and controls have to be in place to reduce the risk of contamination to an acceptable level (which will be within any agreed limits). We have to show that appropriate controls are in place, are working, and are being checked/maintained so that they operate properly.

I presume similar procedures and checks are required in the aviation industry in relation to cabin air supply systems, and that cabin air quality has to meet an agreed standard (thought the standard may vary between Countries/States).

However, it is also important to realise that no system or procedure can ever be 100% foolproof, and that errors or deliberate decisions can be made that lead to system failures.

Given that there is no requirement for passengers’ health to be checked prior to boarding most (if not all flights), there is always the chance that one or more passengers aboard a flight may be carrying a virus (etc), which may or may not be known to them (i.e. in its early stages a virus/microbe may well be virulent yet be causing no identifiable symptoms in the carrier).

I assume cabin air quality standards are designed to manage (i.e. control) levels of airborne contaminants aboard the flight, but I doubt they “sterilise” the air they handle (i.e. actively reduce the level of microbial contamination to zero).

Short of screening passengers prior to boarding (which may well fail to detect illnesses that are not yet causing measurable symptoms), then sterilising all air introduced into the cabin, and then also taking precautions to track the health of all passengers after each flight so that there is a chance of identifying any illness that develops to the point that it can be determined it was present, but not yet detectable, during the flight, I can see no way of ensuring that “good health” can be guaranteed.

And anyway -what do you mean by “good health”?

Do you mean an environment where no-one aboard the plane has any chance of catching any sort of illness/disease?

Or do you mean an environment where the chances of catching such an illness disease are reduced to say 1 in 100, or 1 in 1000 or 1 in 10,000 passenger flights/flight hours/flight legs?

Or does “good health” mean that the flight may leave a small proportion of people aboard (i.e. not more than “n”% carrying an illness they didn’t have prior to boarding, but that the flight will not be introducing any new illness/disease strain into the destination?

And in the last case, how do you allow for the fact that passengers waiting to board any single flight will probably come into contact with passengers waiting to board flights to other destinations in the departure lounge, and similarly may well come into contact with passengers arriving from other starting points as they pass thorough immigration/passport control a their journey ends?

Short of ensuring passengers are tested to prove they are 100% communicable disease free, that they come into contact with no other people or animals except those due to take the same flight (once they too have been certified as 100% disease free), and that all aircraft are boarded via a totally sterile airport environment, and that aircraft retain that sterility in flight via suitable air handling/recirculation/filtration/sterilisation systems then I think we all have to accept that, as in most aspects of our daily lives, we are at a risk of contracting an illness every time we fly.

That said, we have to trust that whomever regulates the airline(s) we choose to fly on set air quality requirements that manage the risk to an appropriate degree (nil risk probably being an un-achievable goal I am afraid!), that the airlines’ staff (flight crew, maintenance engineers etc) operate all systems and procedures properly at all times, that the airliner’s systems operate properly to meet the standards required, and that our fellow passengers (and flight crew) do not fly if they are carrying an identifiable/known transmissible illness!

As with everything in life, it’s a gamble…. is the benefit/outcome of taking the flight worth the risk of contracting some unpleasant illness during the flight? :apologetic:

The usual “shock horror!” media stories about “germ ridden” or “Toxic” ‘planes are often taking a very one-sided view of the problem (don’t forget, they are trying to sell their newspaper/magazine/film!), or they reflect one or two incidents where things went wrong (through equipment failure, human error, or human mis-judgement), and they often forget to mention the vast number of flights where everything worked properly, and no-one aboard suffered any lasting ill-health as a result….

The fact that we have not (yet) seen any major global illness/epidemic spread solely as a result of airline flights, suggests the standards set are probably about right in terms of controlling spread of disease. (And no, I haven’t forgotten SARS and Birdflu!).

As for control of possible engine-originated contaminants there have been a few well documented cases (mineral oil contamination due to leaking oil seals etc), but once a problem is properly identified and confirmed, rather than just base things on a few apocryphal stories, then systems tend to kick in to resolve any common cause.

Paul F

http://www.factnotfictionfilms.com/welcomeaboardtoxicairlines.html
A subject an ex pilot local to us has been on about for a few years

Some food for thought for you good (innovative) aircraft engineers

Here is a not so distant (2012) incident albeit not proven to be bacterial or viral but where the cabin air contamination was a problem.

Some extracts from –

AAIB Bulletin: 5/2013 D-AIRX EW/G2012/10/12 © Crown copyright 2013 See attachment

pp 24 “During the tests the cabin air quality was assessed by an electronic analyser;”
pp 24 “The circulation fans were checked and the recirculation and avionic filters were inspected and replaced. The recirculation filter was later subjected to gas chromatography analysis:”
pp 24-25 “Over the years there have been numerous reviews,studies and research projects on air quality events,conducted in a number of countries. There is a general acceptance that cabin air can be contaminated by compounds released in pyrolysed oil from engines and auxiliary power units.”

1 References and extensive supporting literature can be found in numerous sources, including the 2010 Australian Civil Aviation Safety Authority (CASA) Expert Panel on Aircraft Air Quality (EPAAQ) Final Report, and in the summary report, Health Effects of Contaminants in Aircraft Cabin Air, by Prof Michael Bagshaw, October 2012.

A prolonged economic recession is an ideal opportunity for innovative and professional aircraft engineers (many on this forum) to think of ways to help reduce the impact on the UK’s economy by thinking pro-actively. An economic recession is no different to a big bad war (in fact it is an economic war) and it has been shown that in both great wars Britain innovated and produced a wealth of R&D projects to the benefit of all of us current generations.

Thanks Cking

Pity about the last aspect as random checks on “not so responsible airlines” would be useful at LHR if the necessary hand held tools/instruments were available. Good old fashioned swab sticks would do but the cost of laboratory analysis off site would be astronomical.

On the other hand if random checks were introduced it would act as a deterrent against “not so responsible” airlines.

‘Cutting corners’ especially in this prolonged economic recession is something many “not so responsible airlines” may resort to.

One still sees many pax with face masks travelling out of LHR. Sadly these paper face masks are as useless as having nothing as they rapidly become saturated with human breath including any bacteria and/or viruses carried by the pax.

Who checks that the filters are replaced with correct ones at the recommended time or sooner if contaminated? .

The licenced aircraft engineer who signs for the correct fitment of the recirc fan filters will have checked that they are the correct part number and will also have ensured that it has an approval certificate.

Are these records available in real time to all airport health and safety experts that each aircraft makes a stop at (ideally before the aircraft lands)?.

The maintenance records can be accessed real time by the relevant airworthiness authorities so I’m sure that if health and safety people wanted to see them a quick email would gain them access.

Are there random or regular checks (using e.g. hand held devices, that do not require maintenance operations) on filters and air ducts that are made or can be made, by airport health and safety experts, that aren’t the same checks that are carried out by the airline’s maintenence staff at routine schedules?.

I’ve never seen any.

Rgds Cking (Cough, splutter, sniff :D)

Thanks Amiga 500

A little bit more on the rationale for my opening post.

Who checks that the filters are replaced with correct ones at the recommended time or sooner if contaminated?

Are these records available in real time to all airport health and safety experts that each aircraft makes a stop at (ideally before the aircraft lands)?

Are there random or regular checks (using e.g. hand held devices, that do not require maintenance operations) on filters and air ducts that are made or can be made, by airport health and safety experts, that aren’t the same checks that are carried out by the airline’s maintenence staff at routine schedules?

Why are these and other related questions possibly relevant?

Large numbers of pax are moved for long, medium or short haul periods all enclosed in a presurised cabin (a sealed container).

Aircraft are turned around very quickly for very obvious economic reasons.

Very few of these pax have had any form of adequate medical or health screening before boarding each flight. (dare I say it, some have even forged or obtained for a fee medical vaccination certificates required for entry to the UK)

Bacteria thrive in warm to warmer while viruses can thrive in both warm, warmer, cold and colder environments.

It is not just pax airlines that are affected by this but freighters as well.

There is much recent ado about containers (shipping and air) that are having to be checked very carefully on opening as they bring inside/outside them bacteria, viruses and all manner of small vermin.

Business premises (ie office blocks), hospitals, nursing/care homes, public transport are all potential harbours for bacteria and viruses to thrive in.

Why do these issues become more relevant – prevention is better than cure certainly in the UK, otherwise the NHS bears the burden. UK citizens lose time at work, school, college and university if they develop infections.

Is in-cabin air circulation/re-circulation managed to maintain good health?

Yep.

Off the top of my head, you have to have a 50% air cycle every 90 seconds (that is, effectively replace or filter the entire volume of the cabin every 180 seconds). Mostly its a 50:50 split between fresh air and filtered air.

I can check the CS25 requirements for you later, or even dig up some of my older work, but its something like that.