# Oxygen masks on planes



## hansov (29 Nov 2007)

A question I have always wanted to ask, and need I say, I didn't want to find out the answer from experience . 

Before take-off cabin crew always tell you that "in the event of a sudden drop in cabin pressure, an oxygen mask like this will fall from overhead". Say you are sitting in a row of three seats - how many masks fall? Three or four? And I ask this as they always say "attend to your own mask first before...." If there are only three, if all seats are occupied by adults and if one of those adults has a baby in their arms.......????


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## bacchus (29 Nov 2007)

hansov said:


> Say you are sitting in a row of three seats - how many masks fall? Three or four



AFAIK, there is one extra per row.


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## Miles (29 Nov 2007)

Was watching Air Crash Investigation one night on Discovery. Apparently there is only 15 minutes oxygen available anyways!


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## hansov (29 Nov 2007)

Well I suppose the pilot should be able to correct things in 15 minutes by coming to a lower altitude or indeed landing.


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## hansov (29 Nov 2007)

bacchus said:


> AFAIK, there is one extra per row.


 If thats the case, hopefully a couple with twins are not beside one another.


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## gocall01 (29 Nov 2007)

There are 4 O2 masks for 3 seats.
Asked the question when my wife and I each with a child were not seated in the same side of the aisle.
This was the reason given.


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## bacchus (29 Nov 2007)

hansov said:


> If thats the case, hopefully a couple with twins are not beside one another.


 
That's correct, they can not seat together.


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## efm (29 Nov 2007)

hansov said:


> Well I suppose the pilot should be able to correct things in 15 minutes by coming to a lower altitude or indeed landing.


 
Is this an airline euphemism for falling screaming from the sky as bits are stripped of the plane from the velocity of the descent and crashing into a deserted mountain and perishing in a ball of flame?  

No?


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## landlord (29 Nov 2007)

correct... 4 oxygen masks per three seats. Chemically generated oxygen lasts for 15 minutes.  Once the cabin altitude reaches 10,000 ft or rises at a significant rate due rapid or slow decompression we initiate an emergency decent. From a cruising altitude of 39,000 ft at a descent rate of 5,000 ft per minute (with speed brake out) it will take approximately 6 minutes to reach 10,000 ft where the air becomes breathable again.


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## woodseb (29 Nov 2007)

landlord said:


> correct... 4 oxygen masks per three seats. Chemically generated oxygen lasts for 15 minutes. Once the cabin altitude reaches 10,000 ft or rises at a significant rate due rapid or slow decompression we initiate an emergency decent. From a cruising altitude of 39,000 ft at a descent rate of 5,000 ft per minute (with speed brake out) it will take approximately 6 minutes to reach 10,000 ft where the air becomes breathable again.


 
....and then they just open the window?


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## EvilDoctorK (29 Nov 2007)

woodseb said:


> ....and then they just open the window?



 - You can breath normally at a cabin altitude of 10,000ft - there's sufficient oxygen at that level so no oxygen masks required


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## Guest127 (1 Dec 2007)

heard that the cause of a crash in greece last year was because ground crew didn't connect the air cylinders up to the system before take off. so when the aircraft decompressed and the masks fell down there was nothing in them. greek air force was sent up to see if they could find out what was happening but afaik they reported that the pilots etc were slumped over the controls. frightening scenario. especially for someone enjoys getting away a  few times a year and doesn't mind flying.
on the same subject -only different - has anyone every survived a plane crash over the sea?


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## z109 (1 Dec 2007)

cuchulainn said:


> on the same subject -only different - has anyone every survived a plane crash over the sea?


http://en.wikipedia.org/wiki/Ethiopian_Airlines_Flight_961
Many of those who died did so as a result of drowning through inflating their lifejackets while in the plane.


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## AlastairSC (2 Dec 2007)

EvilDoctorK said:


> - You can breath normally at a cabin altitude of 10,000ft - there's sufficient oxygen at that level so no oxygen masks required



But how does it get in to a sealed cabin? It has to be sealed, remember, to pressurise and hold air as the aircraft climbs.


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## ClubMan (2 Dec 2007)

Miles said:


> Was watching Air Crash Investigation one night on Discovery. Apparently there is only 15 minutes oxygen available anyways!


At least it'll keep you conscious so you can enjoy the crash!



cuchulainn said:


> has anyone every survived a plane crash over the sea?


Or as the safety card puts it - "in the event of *landing ON *water..."


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## orka (2 Dec 2007)

Miles said:


> Was watching Air Crash Investigation one night on Discovery. Apparently there is only 15 minutes oxygen available anyways!


 


cuchulainn said:


> heard that the cause of a crash in greece last year was because ground crew didn't connect the air cylinders up to the system before take off. so when the aircraft decompressed and the masks fell down there was nothing in them. greek air force was sent up to see if they could find out what was happening but afaik they reported that the pilots etc were slumped over the controls.


 
This greek aircrash was probably the one that Miles was referring to. It wasn't that the ground crew didn't hook up the air cylinders - some maintenance work the previous day had required the cabin pressurisation system to be set to manual rather than auto and it wasn't switched back - and the captain didn't notice this in his pre-flight checks. So, the aircraft didn't pressurise at all and when it reached 10,000ft, warnings went off which the captain misinterpreted - and he wasn't aware that the oxygen masks had dropped in the passenger cabin. By the time ground engineers asked the captain to check the pressurisation switch was set to auto, he was a bit zonked from lack of oxygen and didn't understand what they were saying. So, everyone drifted off into unconsciousness (they were all technically still alive when the plane hit the ground) after their 12/15 mins of oxygen was used up and the plane eventually crashed when it ran out of fuel - probably all very peaceful for them really. Except for one poor cabin steward (deep sea diver so probably used to using less oxygen) - he managed to stay alive by using 4 portable oxygen tanks on board - and was seen by the greek air force pilots at the controls (he was also a trainee pilot) just before it crashed after circling for 2-3 hours - he couldn't communicate with the ground as the radio frequency was still set to the take-off airport and he couldn't/didn't know how to change it. Can't have been much fun for him particularly as his fiancee was also a stewardess on board.


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## landlord (2 Dec 2007)

AlastairSC said:


> But how does it get in to a sealed cabin? It has to be sealed, remember, to pressurise and hold air as the aircraft climbs.



The cabin isnt quite sealed in the way you might think.  Actually atmospheric air is allowed into the cabin, by air inlets where it passes through air conditioning units and then out through an outflow valve.  By adjusting the rate of flow of the exiting air you can control the pressure of the aircraft. Closing this valve means air entering the cabin has no where to go and so pressure increases and vice versa. As the aircraft climbs the valve closes and this pressurises the aircraft to a similar pressure to that at ground level. 
In an emergency decent when you reach 10,000 ft the air entering the aircraft through the air inlets is already at a sufficient pressure for the passengers to breathe normally. Hope that explains it.......


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## ClubMan (2 Dec 2007)

orka said:


> some maintenance work the previous day had required the cabin pressurisation system to be set to manual rather than auto and it wasn't switched back - and the captain didn't notice this in his pre-flight checks.


Or the co-pilot? Sounds like a gross pilot error to me? Was there ever any investigation?


> So, everyone drifted off into unconsciousness (they were all technically still alive when the plane hit the ground) after their 12/15 mins of oxygen was used up and the plane eventually crashed when it ran out of fuel - probably all very peaceful for them really.


Yeah - they were better off. Didn't know about the other poor chap!


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## Jock04 (3 Dec 2007)

cuchulainn said:


> on the same subject -only different - has anyone every survived a plane crash over the sea?


 
Not sure about fixed wing, but I'm here to tell you that you certainly can in helicopters....


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## EvilDoctorK (3 Dec 2007)

AlastairSC said:


> But how does it get in to a sealed cabin? It has to be sealed, remember, to pressurise and hold air as the aircraft climbs.



It's not sealed   - as far as I know the pressure is maintained through the forwards motion / engine power of the aircraft compressing the outside air and putting into the cabin and it's vented out at a controlled rate to maintain the pressure at the desired level in the cabin


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## hansov (3 Dec 2007)

The things I learn on askaboutmoney  Now I'll probably never fly again  . Thanks guys!


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## ClubMan (3 Dec 2007)

Why? It's still by far one of the safest ways to travel as far as I know. You are much more likely to die in a car crash on your way to/from work for example! Hope that cheered you up!


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## Guest127 (3 Dec 2007)

ClubMan said:


> Or as the safety card puts it - "in the event of *landing ON *water..."


 


Jock04 said:


> Not sure about fixed wing, but I'm here to tell you that you certainly can in helicopters....


 
That's about it as far as I can see. I know where a few aircraft have gone off the runway into the sea and also saw footage of a plane trying to land near a beach but it too crashed. (might well be the one Yoganmahew refers to) wouldn't think there was any chance of survival in mid ocean as the swell would be too much for an aircraft to take on landing.


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## Thirsty (3 Dec 2007)

Flew on South African Airline Kuala earlier this year;  the cabin crew while doing the safety talk advised

 "if you are travelling with a child, please fix your mask first, and then the child's ...if you are travelling with more than one child - pick your favourite!"


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## WhoAmI (5 Dec 2007)

The reason you are told to attend to your own mask first is that a reduction in oxygen levels won't asphyxiate you (immediately!), but will instead make you giddy and decrease co-ordination, so that you mightn't be able to do your mask later.


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## dmac (10 Dec 2007)

I was flying from Toronto to Dublin earlier this year with a budget airline, when we got to Hamilton airport there were masses of people everywhere, and looking at the screens we could see that loads of flights from this carrier where either delayed or cancelled, luckily our flight had an on time status. I checked in and went through security and found that there where people waiting in the departure lounge all day trying to get to Glasgow and Manchester, eventually our flight got delayed 1 hour, and the Glasgow one was cancelled, there was no one of authority to tell anyone what was going on and the Manchester people had been waiting 7 hours at this stage at 10.30pm a voice came over the intercom to say that both the Dublin and Manchester flights would get away and the problem was with the planes computers, after another hour we were told to board and the Manchester people where told, that because of storms over Iceland and Greenland they where getting it difficult to get a flight path over land in case they had to make an emergency landing.
Can you believe they said something like that


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## Guest127 (10 Dec 2007)

just back from a footie weekend in Leeds and thanks to this posting , actually paid attention to the flight attendant last night when she was demonstrating the inflation vest. For the first time I noticed that when she was indicating the doors that she had to use 'reverse' hands to point out the doors ie when pointing to doors over the left wing she was using her right hand, makes sense I know as she was facing us but never noticed it before. maybe the fact that it was quite windy also concentrated the mind but it was relatively smooth.


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## reds (10 Dec 2007)

You also have to pull down on those masks to activate the oxygen flow. 
Worth remembering!


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## ClubMan (10 Dec 2007)

reds said:


> You also have to pull down on those masks to activate the oxygen flow.
> Worth remembering!


If you ever have to remember this then you probably won't be posting here again about it. Or anything else!


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## davidoco (12 Dec 2007)

orka said:


> This greek aircrash was probably the one that Miles was referring to. It wasn't that the ground crew didn't hook up the air cylinders - some maintenance work the previous day had required the cabin pressurisation system to be set to manual rather than auto and it wasn't switched back - and the captain didn't notice this in his pre-flight checks. So, the aircraft didn't pressurise at all and when it reached 10,000ft, warnings went off which the captain misinterpreted - and he wasn't aware that the oxygen masks had dropped in the passenger cabin. By the time ground engineers asked the captain to check the pressurisation switch was set to auto, he was a bit zonked from lack of oxygen and didn't understand what they were saying. So, everyone drifted off into unconsciousness (they were all technically still alive when the plane hit the ground) after their 12/15 mins of oxygen was used up and the plane eventually crashed when it ran out of fuel - probably all very peaceful for them really. Except for one poor cabin steward (deep sea diver so probably used to using less oxygen) - he managed to stay alive by using 4 portable oxygen tanks on board - and was seen by the greek air force pilots at the controls (he was also a trainee pilot) just before it crashed after circling for 2-3 hours - he couldn't communicate with the ground as the radio frequency was still set to the take-off airport and he couldn't/didn't know how to change it. Can't have been much fun for him particularly as his fiancee was also a stewardess on board.



thats unreal. Shows that a little knowledge is a dangerous thing. And the fiancee, that's just cruel. Should he have flow over the sea, opened one of the doors and jumped at x altitude. On another crash in japan in the early 90s up to 10 people survived when the plane hit a mountain but the rescue services waited until daylight to go to the site and most of em died during the night. Ps they were sitting in the very back of plane.


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## Guest127 (12 Dec 2007)

Billy Connolly: always ask for a set at the back because  _'planes don't reverse into mountains. _


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## jmayo (20 Dec 2007)

You should be able to breath at altitudes above 10,000 ft, but the higher you go the more chance you will not have enough and you will get confused and do stupid things.  So even if you only get down to say 15,000 ft you should be ok. 
Why would this be important point, well 10,000 ft through the Alps, Andes, Rockies etc would be a little dangerous.

Speaking of losing cabin oxygen, that is what happened to the private jet belonging to the golfer Payne Stewart a few years ago. 

I was once on flight where just on climb out the oxygen masks dropped above us.  We were at the back but enough people spotted it and there were a few shocked looks.
We of course were told not pull them.
They sealed them back up with sticky tape, so we would have to pull the tape if there was a real emergency.


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## HighFlier (20 Dec 2007)

Economist Magazine Oct 2006 :"In the entire history of aviation the number of widebody aircraft to successfully land on water is zero"

All these lifejackets and demonstrations are to make you feel good.


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## orka (20 Dec 2007)

HighFlier said:


> Economist Magazine Oct 2006 :"In the entire history of aviation the number of widebody aircraft to successfully land on water is zero"
> 
> All these lifejackets and demonstrations are to make you feel good.


 
The number of totally successful water landings may be zero but there have been water crash-landings with survivors - although ironically the lifejackets may kill rather than save.  In 1996 a hijacked ethiopian airlines 767 landed (and was captured pretty spectacularly on video from a nearby beach - youtube has it) close to some islands.  The video makes it look like it disintegrated totally but one-third of passengers and the 2 pilots survived. 123 of the 175 passengers and crew members were killed, as well as all three hijackers. Many of the passengers who died survived the crash but they had disregarded the captain's warning not to inflate their life jackets inside the aircraft, causing them to be 'pushed' against the ceiling of the fuselage by the inflated life jackets, unable to escape, and drowned. An estimated 60 to 80 passengers, strapped to their seats, presumably drowned.  The survivors were helped to safety by people on the nearby beaches.


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