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Air supply nozzles and Covid-19

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Air supply nozzles and Covid-19

Old 24th May 2020, 08:53
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Air supply nozzles and Covid-19

EASA apparently recommends that, in general, operators should "Reduce the use of individual air supply nozzles as far as possible".

Page 13 https://www.easa.europa.eu/sites/def...gers_final.pdf


Elsewhere there are suggestions that passengers should use the nozzles to ensure that they are breathing a supply of recently filtered air.

Comments ?
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Old 24th May 2020, 09:44
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I always think it helps, when telling people what to do or what not to do, to say why. EASA say "Reduce the use of individual air supply nozzles as far as possible" but don't give any reason. Why might they say that? Might they think that ambient air in the cabin is less infective than air coming from the nozzles?
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Old 24th May 2020, 10:40
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Around 50% of air in the cabin is recirculated air drawn out of the cabin at floor level and through ducts goes through filters then the recirculator fans before joining with new air from Pneumatic supply in the mixing duct. The filters prior to this Covid problem were replaced as routine maintenance, now though I think the regulators ought to change and enforce replacing these filters more often, either by a reduced number of flight cycles or reduced number of flight hours. Contaminated recirc filters and the whole aircraft is then contaminated, need more than small masks to stop the spread as the virus can linger in the eyes for a fair number of hours.
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Old 24th May 2020, 11:11
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Who says these filters actually filter airbourne viral contamination 100% or even at all?
I think you have to assume that all of the a/c air supply is contaminated to some degree. Therefore closed vents should be marginally safer.
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Old 24th May 2020, 12:17
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Sorry to burst your collective bubbles, but cabin air filters won't filter down to 0.1 micron (which is the particle size of the virus) they are there to prevent dust and lint build up, or are there to protect sensitive equipment (like outflow valves reference lines)

Even if all the individual 'punkah vents' are closed, then the relieving valves (nothing fancy, just spring loaded flaps) in the ductwork ( behind overhead bins usually) will open , and that air will come into cabin anyway.

So, open or closed, will make no difference to air coming in to cabin, but closed will reduce chance of a direct blast to the face.

Ttfn
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Old 24th May 2020, 13:41
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I wonder if the concern might be that the higher velocity air stream from a nozzle could blow droplets from the passenger further away within the cabin.
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Old 24th May 2020, 13:48
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[QUOTE=ivor toolbox;10791916]Sorry to burst your collective bubbles, but cabin air filters won't filter down to 0.1 micron (which is the particle size of the virus) they are there to prevent dust and lint build up, or are there to protect sensitive equipment (like outflow valves reference lines)

Even if all the individual 'punkah vents' are closed, then the relieving valves (nothing fancy, just spring loaded flaps) in the ductwork ( behind overhead bins usually) will open , and that air will come into cabin anyway.

So, open or closed, will make no difference to air coming in to cabin, but closed will reduce chance of a direct blast to

i try to avoid bubbles.

If you have access, go and have a read of OIT 999.0008/20 or ISI 21.00.00119

a bit of info. All of the air in Airbus cabins is, on average, completely changed every 3 minutes(during cruise) - even after taking account of filtered and recirculated air. This is a much higher rate of flow than people experience in other indoor environments, and means that passengers are provided with about 80 times as much air as they need to breathe.



The air in Airbus aircraft cabins is a mix of fresh air drawn from outside, and air that has been passed through extremely efficient filters, which remove particles in the air down to the size of microscopic bacteria and virus clusters (with an efficiency of better than 99.99 per cent). These filters called High-Efficiency-Particulate Arrestors (HEPA) have been shown in tests to provide air that meets the standards set for hospital operating theatres. particles within the size range of typical Viruses are captured by the HEPA filters with in excess of 99.99% efficiency


COVID-19 is approximately 0.125 micron (125 nanometers) in diameter. It falls squarely within the particle-size range that HEPA filters capture with extraordinary efficiency: 0.01 micron (10 nanometers) and above

Id prefer to be on the plane...
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Old 24th May 2020, 13:50
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Originally Posted by ivor toolbox View Post
So, open or closed, will make no difference to air coming in to cabin, but closed will reduce chance of a direct blast to the face.
Ttfn
I dont quite agree with that. The Punkah vents will be directing a flow normal directly at a person, whereas other flows will be more diffuse, reducing the airflow directly over a person, and also allowing contaminated vapour to land elsewhere.
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Old 24th May 2020, 15:12
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Originally Posted by 320busboy View Post
If you have access, go and have a read of OIT 999.0008/20 or ISI 21.00.00119

a bit of info. All of the air in Airbus cabins is, on average, completely changed every 3 minutes(during cruise) - even after taking account of filtered and recirculated air. This is a much higher rate of flow than people experience in other indoor environments, and means that passengers are provided with about 80 times as much air as they need to breathe.

The air in Airbus aircraft cabins is a mix of fresh air drawn from outside, and air that has been passed through extremely efficient filters, which remove particles in the air down to the size of microscopic bacteria and virus clusters (with an efficiency of better than 99.99 per cent). These filters called High-Efficiency-Particulate Arrestors (HEPA) have been shown in tests to provide air that meets the standards set for hospital operating theatres. particles within the size range of typical Viruses are captured by the HEPA filters with in excess of 99.99% efficiency

COVID-19 is approximately 0.125 micron (125 nanometers) in diameter. It falls squarely within the particle-size range that HEPA filters capture with extraordinary efficiency: 0.01 micron (10 nanometers) and above

Id prefer to be on the plane...
Which would suggest that the EASA advice is misleading ?
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Old 24th May 2020, 22:14
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Originally Posted by occasional View Post
Which would suggest that the EASA advice is misleading ?
Which would suggest all aircraft are not the same. Thats the info on brand A. Brand B / MD /sukhoi / regionals and others may be different.



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Old 25th May 2020, 06:46
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Originally Posted by 320busboy View Post
Which would suggest all aircraft are not the same. That’s the info on brand A. Brand B / MD /sukhoi / regionals and others may be different.


Have any aircraft manufacturers made the relevant recommendations ?

Last edited by occasional; 25th May 2020 at 08:11.
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Old 25th May 2020, 08:19
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Originally Posted by occasional View Post
Have the aircraft manufacturers made the relevant recommendations ?
Airbus
OIT 999.0008/20 and ISI 21.00.00119.

Gasper vents are an option. Not all aircraft have them. As per the post I made earlier, the air coming out is 99.99% filtered from bacteria. Better than 0% filtered from the people near you. For the drivers, depends which airbus model your in depends if you get any recirc air mixed or not in the cockpit.

As the cabin airflow is designed with a top down flow, it doesnt make sense to me to care whether you use gasper on airbus or not as the Air is clean. More fresh air seems to be a better option. However like all the information people can believe what they choose to. Just sharing the facts from product A.
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Old 25th May 2020, 08:35
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Originally Posted by hoss183 View Post
Who says these filters actually filter airbourne viral contamination 100% or even at all?
The manufacturers do. It's HEPA filters same as used in hospital sterile surgery rooms. Filters best compared to anything else.

Together with the fact that the air sourced from the engines is about 260C before conditioning and the aircraft flies at altitude, for airborne contamination - speaking of air quality - aboard a modern jet in flight is as safe as it gets.
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Old 25th May 2020, 09:01
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EASA is not being misleading. The individual pax vents are recommended to be turned to reduce (but not eliminate) flow of air - especially around a symptomatic passenger - to stop the viral particles being blown further afield.

The natural flow of air is from above and drawn in at the feet. (in an Airbus anyway). HEPA filters (insert best JC Flying circus voice) "as used in 'ospitals" are actually very very good at filtering out COVID sized particles.
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Old 25th May 2020, 09:32
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Originally Posted by compressor stall View Post
EASA is not being misleading. The individual pax vents are recommended to be turned to reduce (but not eliminate) flow of air - especially around a symptomatic passenger - to stop the viral particles being blown further afield.
But that advice is very suspect. It would appear that in an A320 all the passengers should have the nozzles at full blast directed towards their face and in that way nobody would get infected.
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Old 25th May 2020, 11:26
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Originally Posted by compressor stall View Post
EASA is not being misleading. The individual pax vents are recommended to be turned to reduce (but not eliminate) flow of air - especially around a symptomatic passenger - to stop the viral particles being blown further afield.

The natural flow of air is from above and drawn in at the feet. (in an Airbus anyway). HEPA filters (insert best JC Flying circus voice) "as used in 'ospitals" are actually very very good at filtering out COVID sized particles.
If your infected and breathe horizontally into a stream of mostly downward vertical medium velocity air Id tend to think it would help the downward journey toward the bilge for recirc.

added to the already downward overall flow (is why you only smell a fart for a fraction of the usual marinating time) then it would only help it.

if your hot, use it. If your not, dont. The quality of the air is better than the terminal you walked through and the bus or taxi you arrived in.

Or you can email them to clarify why they make that statement.

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Old 27th May 2020, 11:23
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Originally Posted by 320busboy View Post
Or you can email them to clarify why they make that statement.
The intention is apparently to reduce propagation of the virus from an infected person. They are apparently being "guided by scientific advice" - not a phrase which inspires much confidence.

Anyone know how efficient the filters are on a 737-800 ?
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Old 27th May 2020, 12:01
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Originally Posted by occasional View Post
The intention is apparently to reduce propagation of the virus from an infected person. They are apparently being "guided by scientific advice" - not a phrase which inspires much confidence.

Anyone know how efficient the filters are on a 737-800 ?
Thats my point, just assume they're not and put yourself in the best case scenario.
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Old 27th May 2020, 12:10
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Direct from Airbus overnight in a COVID-19 information package...

The use of passenger individual air outlets should be minimized
It's pretty straight forward I'd have thought. The flow of air is top to bottom. That's great for minimising the spread of particles - they fall to the floor and stay in a small radius around the infected person. Having pax nozzles on high can cause eddies and other currents and blow the particles further afield. Somewhat related, Airbus also recommend not to encourage natural ventilation on the ground (windows and doors) as it also disrupts the flow of air - from top to bottom.
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Old 27th May 2020, 12:48
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320busboy did you read your own link that throughly? I have NO problem about the filtering capability of the HEPA filters, I do with the fact that you believe that it's completely safe in an aircraft (well, AB anyway) than anywhere else, but I'm not so sure about that. For starters the OIT is a RECOMMENDATION, there appears to be no requirement on filter replacement by the AMM, operator discretion! As is whether the operator even passes on the OIT is at their discretion.

One other area of concern I'd have is that while the HEPA filters are designed to take viruses out of the air, what are the AMM RECOMMENDATIONS for replacement based on? I doubt that the aircraft designers had expected that they would be needing to remove viruses like CV19 so I doubt they have accurate data for this as well (by this at what point of contamination do you replace them based on risk of transmission) . Regardless how some on PPRuNe wish to feel because of the impact on their careers and financial positions, this virus is nothing like the seasonal flu. I also wonder what the cost of the filters are and how that plays on management when it comes to this issue. If it isn't mandatory I bet it isn't replaced.

Last edited by exfocx; 27th May 2020 at 13:01.
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