Planes....

[Jim GM4DHJ ...]

Do you think that in planes they have switched from recirculation to fresh air yet ?

[Tim+]

Hmm, nice idea but I suspect the bean counters will say no.

Tim

[Graham.]

HEPA filters, so nothing to worry about. Apparently.

[The Natural Philosopher]

All planes use fresh air anyway

[harry]

Oh yes there is. The air is bled from the first stage of the turbine and contains oil vapour.

[harry]

[turnipt fucker]

Not in the sense that none of it is recirculated they don?t.

[Tim+]

?

The air comes from the engines and is recirculated (via filters) but the number of air exchanges per hour is determined by bean counters. More exchanges means higher fuel consumption.

If you?re sat in a tin can with hundreds of other sneezing folk, the air exchange rate has a significant effect on the air quality. You?ll probably inhale others folks exhalations long before the air has had a chance to be filtered.

Tim

[Andrew]

Until you travel on a plane where the engine filters fail allowing nasty smoke into the cabin.

[Andrew]

No they don't. 90% of it is recirculated. Only 10% 'fresh'; is mixed in because heating it up from -60C or whatever uses up fuel. Thats why there have been cases of nasty smoke entering the cabin when the heating unit in the engines has a fault.

[The Natural Philosopher]

Dint be stupid. There is no cost that is measurable tapping a few cu ft of air from an engine compressor in a minute compared with the tens of cu m each second passing through it.

Well yes.

[The Natural Philosopher]

Not really. There is a ton of waste heat in the engines anyway. It isnt hard to have a small heat exchanger near the fan exhaust

And on at lests onbe aircraft I s on te cabin was heated by electrical elements behind te walls anyway, driven by the gebby on one opf the engines

That's why there have been cases of nasty

Oh dear. You simply haven't understood.

When the oil pump on the jet compressor has leaked oil into the inlet of the air system you mean.

Which wouldn't happen if it was massively recirculated.

[Tim+]

From

Quote:

?In early commercial jet aircraft, passenger cabins were ventilated with

100% outside air. In more recent jet aircraft, approximately 50% of the ventilation air is outside air and the remaining 50% is filtered recirculated cabinair. The reason for using recirculated air is quite simple- fuel savings. From the document Commercial Airliner Environmental Control System- Engineering Aspects of Cabin Air Quality: ?

Tim

[John_j]

But there currently isnt any evidence that you catch this virus by breathing the exhaled air of those that are infected with it. Lots of evidence that its pass be bodily fluids and droplets etc.

[The Natural Philosopher]

where it shows that zero recirculation simply give 0.7% greater fuel consumption

I am surprised that they are chasing that.

[Brian Gaff (Sofa 2)]

Its normally a bit of both in fact. Air comes in someway through the compressor chain at which time its warm at least, though fume events can occur which is worrying. Of course the higher you go the less oxygen there is about. Brian

[alan_m]

There was a report on Radio 4 the other days about aircraft staff campaigning about the dangers of toxic substances entering the aircraft from the engine air bleed and serious occurrences were more common than the "industry" admitted. Aircraft crew stating that it was happening and aircraft manufacturers denying or playing down the seriousness

[The Natural Philosopher]

Yes, but smoke it ain't.

The feeds are all from the jet engine compressor, which compresses and heats the air (no extra heating required). If however the bearing oil seals (or whatever the equivalent is on a jet engine) are ratty then engine oil can get in as well. Under compression that will probably vapourise.

[alan_m]

[Tim+]

Not by simply breathing exhaled air, no. But people sneeze, and it?s almost impossible not to send out a spray of droplets, some of which will settle quickly, some will float around. Exchanging the air more often will reduce the floating virus load.

Tim