Air-Con or Con-Air

The idea of using air-con or recycled air has never appealed to me. Perhaps it goes back to my younger days when I lived on a very hot island and we had to acclimatise as quickly as possible and this was best achieved by the use of slatted windows, fly screens and natural shelter. The “luxury” of air conditioning was restricted to the pilots and cabin crew that flew back and forth, who due to their limited time on the island had limited chance to acclimatise.

In recent years I became sceptical about the air-con units in buildings (reported risks of Legionella) and this distrust was also applied to the recycled air in passenger carrying airliners. Don’t get me wrong, I have flown more times than I can remember and have no fear of flying, in fact I include the flying part within any holiday as part of it, with the holiday starting the minute the suitcases are checked in at the airport.

It was on a recent short haul flight that events got my mind thinking about what if anything was going on within the aircraft recycled air system and whether this could account for head colds and chest infections which often occurred after a holiday abroad. You only have to watch CNN or BBC World News to see people around the globe wearing ‘smog masks’ as they walk along streets or while travelling on public transport to get an idea that something somewhere is affecting people’s health and I wanted to know if travelling on aircraft increased that risk.

On this particular flight, just after take-off as the aircraft levelled out and the cabin crew were about to commence the refreshments service, that an announcement was made which informed everyone on board that “a passenger on this flight has an acute allergy to nuts, so please do not eat any nuts or any food containing nuts, as the particles can be recycled around the cabin”. My immediate thoughts were that I hope the passenger has got their Epi-pen with them. Almost immediately, to my left was another member of the cabin crew serving a different passenger with his drink and asked him “Would you like nuts with your drink?” This was a tad surreal especially with it being within seconds of the initial announcement being made.

So I began to research aircraft recycled air systems. Was it possible for someone eating peanuts while seated in row 33 to cause adverse effects on someone seated in row 1? How did the air system function?  On the underside of the luggage stowage bins are small manual nozzles which you can pull to activate / push to stop and move them around to direct where you want the air flow to be directed. Are these capable of firing deadly peanut particulates into the airway of a person with an acute nut allergy at 30,000 feet inside a pressurise aircraft? At least there was comfort in knowing that all the cabin crew are trained to a high standard of first aid and the medical equipment includes Oxygen and a comprehensive range of medicine and drugs including medication for the treatment of Anaphylaxia.(I did not learn whether or not the passenger with the “acute allergy to nuts” was actually carrying an Epi-pen).

Bearing in mind that some ‘Budget Airlines’ do not include a meal within the cost of the flight ticket, I then began to consider the knock-on effects that this ‘acute allergy’ might bring about because a high number of passengers travelling on these low cost airlines purchase food and drink in the departure lounge and bring it onto the aircraft when they are called to start boarding. It is most likely that none of these passenger give a seconds thought to whether or not another passenger might have an ‘acute allergy’ to something they have purchased and intend to eat during the flight.

Then there are the larger transcontinental or long haul airlines which include not just a meal but drinks, ice creams, hot face cloths and (if the adverts are to be believed) even hot showers and massages within the price of the flight ticket. The menus on these sky liners are invariably well balanced and prepared in the galley with an option or two. Sometimes the flight is so long that several meals and snacks are served in flight or a refuel stop is made at an intermediary airport. Added to the meals will be the duty free sales and of course the soft drinks, wine, beers and spirits with crisps, nuts and other assorted tasty bites.

At what point therefore should the person with the ‘acute allergy’ inform the airline? It was a bit like bolting the stable door after the horse had bolted with regard to the nut allergy passenger as food and drinks purchased in the departure terminal were already being consumed. If the allergy is actuallyTHAT serious should not the passenger have given adequate and timely notice to the airline staff at the time booking the seats or at the very latest when checking in?

I contacted the Civil Aviation Authority (CAA) and asked them for some information regarding the risk of anaphylaxia on board an aircraft:Unfortunately, cabin crew may not always be informed of a passenger's allergy until passengers have boarded the aircraft. Some airlines will remove certain foods from specified flights if contacted well in advance by the passenger. This does not however address the issue of other passengers bringing peanuts or other nut products on board. Although anaphylactic reactions can occur as a result of inhalation of food particles, they are very rare. It is unlikely that someone opening a packet of nuts four rows down could trigger a reaction, but it might be possible if they were in the adjacent seat.

 So, according to the CAA if a passenger has an acute allergy to peanuts (or some other food stuff) they might react if exposed to it within a seat or two away. But what about the recycled air system? Is it possible for the system to circulate food particles (or aerosol generated bacteria from passengers with an upper respiratory tract infection) around the aircraft which in doing so might place other passengers at risk?

With regard to the aircraft air system I specified the Boeing 737-800 series which is a popular work horse with short haul and low cost airlines. Again the CAA was very helpful and responded:  With regard to the B737 - 800 series aircraft; The circulation of air within aircrafts is segmental and does not travel along the aircraft, research has shown that air movement along the cabin is for no more than 3 rows; any aerosolised nut particles suspended in the air and re-circulated would be removed by the filters in the recirculation system.

This was beginning to look good but I wanted to learn more about aircraft recycled air systems and in particular what was FACT and what wasFICTION. Was this becoming my very own Pandoras Box?

There are references to be found in numerous media sites about aircraft cabin air not being as clean as it should be with exaggerated claims that the recycled air is contaminated with pathogens. So I decided to look into how the air is actually ‘pumped around the aircraft’ and if whether or not that is the correct way to describe it.

The air inside aircraft is apparently a mixture of fresh air AND recycled air with compressed air coming from the jet engines. Although initially the compressed air is hot it does not contain any unwanted particles such as fuel, engine oil or gases. The air is directed into what in the aviation world is referred to as the pneumatic air cycle kit (PACK) and according to one source there are usually at least two packs per air craft.

So here we are, strapped into our seat waiting for the aircraft to be pushed back from the stand so that its jet engines can propel it along the taxiway and ultimately along the runway up into the wild blue yonder. It’s a hot sticky day so even before the air craft doors are shut we note passengers tweaking the air vents above their heads in an effort to keep cool. With the doors securely shut the air must be delivered equally to all outlets and at the same temperature & pressure; but if it doesn’t go somewhere else it must surely go around and around, or does it?

In reality, according to source, the air leaving the vents above your head is not sent back to the front of the aircraft, it is in fact drawn down into the lower section of the fuselage (the cigar shaped bit that we and cargo occupy) where most of it is vented outside to the atmosphere. The air which is not vented to outside is remixed with more compressed air from the engines and makes its way again through the ‘packs’ to the air vents above our heads. By now I was thinking that I had found the cause of illness but I was wrong. The air that enters the lower section of the fuselage passes through filters that are as efficient AND as expensive as those found in clinical areas.

These filters eliminate all particulates and prevent anything other than clean air from re-entering the occupied area of the fuselage; so why do passengers claim that the air-con has been the cause for their subsequent illness? Again my source has a simple answer which is that air conditioned air is very dry which explains why passengers feel dehydrated. Some of us may have experimented by placing a swab moistened with sterile water behind an oxygen mask in an attempt to prevent prolonged use the oxygen supply from drying out or irritating the patients airway; and if you have will know that this simple act works quite well. So why can’t the airlines humidify the air-con so that it not so dry? The simple answer is that it would take thousands of litres of water and with one litre weighing one kilogramme the reason becomes clear. The amount of water needed to adequately humidify the occupied area for the duration of the flight would be too heavy.

So where is this issue about dehydration leading us? Well, although air conditioning units are generally clean, if not used regularly bacteria may develop within it, which is why aircraft air-con is kept running and serviced at every opportunity. The downside is that the air-con can be responsible for drying out the sinuses which in turn can cause the mucous membranes to crack or split which then becomes a route for bacteria to enter the body. So the current thinking is that it is not the air-con which makes us unwell it is when our sinuses dry out as a result of being in an air conditioned environment and our membranes break down so that bacteria can find it easier to enter our bodies and that appears to be the answer.

The solution? It all comes down to basic IPC. The things which are most likely to be the source of our post-flight illnesses are those everyday objects that we normally take for granted but seem to forget when we go away on holiday; gantry handles, door handles, armrests, trays, turnstiles and toilets door handles. Even airline pilots are known to regularly use hand sanitizer  on the instruments, switches and levers in the cockpit before they settle into their pre-flight routines.

To say that aircraft cannot make you ill is not exactly correct because some people will invariably be poor fliers, who find travel difficult at the best of times and these include people who suffer badly on the roller coaster or the waltzer at the fairground. The problem would appear to be that any mass gathering of people in a confined space will increase the risk of spreading a disease and that includes for example cinemas, theatres, train carriages and aircraft.

There have been reported cases of people contracting malaria at airports even when they have never left the country and sadly these people did not benefit from a timely and accurate diagnosis because they “had not travelled abroad”. So with that in mind, how many times have you discounted foreign travel as a potential source simply because the patient had not themselves travelled abroad? Did you ask them if they had been to an airport terminal or met friends / family from abroad? The actual number of reported malaria cases at UK airports is less than 20 confirmed which is very low when compared with over 650,000 aircraft flights that were tested. However, those 20 were enough to warrant a thorough investigation with intensive research to identify the type of mosquito and from which country that had originated. Pause for thought.

Do I have a pet hate? Yes, but it has nothing to do with aircraft air-con or recycled air.. The recent decision to start charging 5p for every plastic bag that is handed out at supermarkets is, I believe taking the wrong step. From a hygiene point of view I would rather see disposable gloves provided where fresh food products are on sale and for it to be mandatory that all shoppers wear them when handling fresh fruit and vegetables. It works very well in other countries and takes away the worry that the food has just been handled by someone who did not bother to wash their hands after using the toilets.

The old adage “coughs and sneezes spread diseases” still rings true today, so what we need to do is “catch it, bin it, kill it” by using tissues; but most importantly we need to promote the importance of hand washing with soap and hot water as well as the use of hand sanitizers.

Jeff Pittman