Air in cabin

[alvcheng]

Is the air in the cabin fresh?
How do airplanes maintain fresh air in cabin?

[Greg]

it's ducted from the engine so it is fresh in the sense it isn't pre-packaged. The new planes recirculate it more though because it's cheaper. better gas mileage.

[Airigami]

How do airplanes maintain fresh air in cabin?

By not serving too much curry or baked beans.

The more digestive-friendly foods served, the fresher the air.

Ooo - my 100th post. And what a tasteful way to bring it up (or let it out as the case may be).

[MCIFLYR]

Well, on the ground, there is a large hose fitted to a port in the fuselage that is not recirculated. This provides heat and A/C from usually the jetway's unit or an air cart parked next to the plane. In the air, the aircraft uses it's own A/C units, and on most older aircraft, the air is recirculated i believe. I'm 100% sure on the ground the air is 100% fresh, but in the air, i dont know the specs for all aircraft.

[egll]

Could someone explain the following please?

On the last few times I've been on a 747 I have found it to be very hot and stifling in the Y section, this has happened in various climates-from the heat of Singapore to coolness of a winter evening in London. But on every occasion the cabin has cooled within around 30 minutes of take off. This has only been noticeable on BA aircraft, I went on a QF743 last month and didn't notice this problem.


Matt

[Greg]

Some planes are so big they create their own weather in different places.

[Thomas_Cook_757-200]

Hi,
The cabin air system controls air flow, air filtration and temperature.
Aircraft operate with a mixture of 50 per cent outside air and 50 per cent re-circulated air, and air circulation is continuous. All of the air in the cabin is replaced by the incoming mixture of outside air and filtered air every two to three minutes, depending on aircraft size.

Thanks

Thomas_Cook_757-200

[Colin Parker]

In the air, the air that is filtered and recycled, runs through HEPA filters, which remove 99.97% of all particles. If you are worried about SARS, don't be. The large size of the SARS virus means that it cannot travel through the filters, so the air is clean regardless of whether it comes from outside, or is recycled.

On the ground, the APU is normally good enough to cool the entire aircraft, including the back of the plane. However, if the aircraft has been sitting around all day, it is likely that to save money, there was no air recirculating around the cabin, and therefore it is likely the entire aircraft gets hot. When the APU is finally started, the back section takes the longest to cool down.

Another possiblity is that ground air was being used. To save APU life, or if the APU is unserviceable, ground air is used from ground based airconditioning units. These provide air straight into the pack systems of the aircraft. However they are not normally very good and do very little to cool the back of a long aircraft like a 747 or 777. By the time you are flying, the engines have been providing the air for some time, so they whole aircraft has no problem maintaining whatever temperature is demanded in that zone.

[DeltaCappy]

The cabin environmental control system on modern aircraft is automatic and is designed by the manufacturer to comply with requirements of the FAA, CAA and JAA. The specification is determined by the regulatory authority and the aircraft manufacturer, not the airline. The total volume of air is exchanged every 2 to 3 minutes and the system provides approximately 20 cubic feet per minute per passenger. Of this, the volume of conditioned fresh air per passenger is about 10 cubic feet per minute, and approximately 10 cubic feet per minute is re-circulated and passed through high efficiency particulate filters to remove bacteria and viral particles. These HEPA filters are 99.99% efficient and are the same as those used in hospital operating theaters. Independent published research shows that the concentration of biological micro-organisms in an aircraft cabin is much lower than in an ordinary city location or on other modes of public transport such as buses and trains. A report published by the World health Organisation states '...investigations of possible transmission of [infectious disease] on aircraft found no evidence that air re-circulation facilitated transmission of [infectious disease] aboard aircraft....' Oxygen concentration in the air is 21% at all altitudes, but the total air pressure falls as altitude increases. The cabin is pressurised to maintain a cabin altitude of around 6000 feet irrespective of the actual altitude of the aircraft. There is more than enough oxygen available for human consumption at cabin altitudes up to 8000 feet, unless an individual is suffering from certain diseases of the heart or lungs. In this case, supplementary oxygen can be provided if prior notification is given to the airline. Carbon dioxide is a product of normal human metabolism. The concentration in the cabin varies with fresh air rate, the number of people present and their degree of physical activity. The minimum ventilation rate to meet the ASHRAE acceptable limit of 2,500 parts per million is 5 cubic feet per minute per person. Current fresh air rate in wide bodied aircraft is 10 cubic feet per minute per person, i.e. twice the minimum required.

[MeltedPixel]

I dont know if it did in 1992.
I was 2 and took a crap on my dads lap in the middle of a flight.
Stunk the whole place up for a 5 hour flight.