What are oxygen tanks doing in the cargo holds of airplanes anyway?

That hole in the side of the Quantas jet last week was caused by an exploding oxygen tank that was stored in the cargo hold of the plane. Why are oxygen tanks in the cargo hold in the first place?What are oxygen tanks doing in the cargo holds of airplanes anyway?
When you flew, do you remember this little safety speech about ';in case of cabin depressurization, and oxygen mask would fall from the ceiling'; bit?


There are two ways to have oxygen in such conditions:


1- though oxygen generators (canisters filled with chemicals that react together and release pure oxygen when activated)


2- oxygen tanks





Regulations require that pilots have a more reliable source of oxygen than passengers do (above a certain altitude, if a pilot has to be left alone, he has to don an oxygen mask); and since canisters release a lot of oxygen but only for a few minutes, this calls for the presence of oxygen tanks.What are oxygen tanks doing in the cargo holds of airplanes anyway?
Hahaha... some of the answers here really crack me up.





The o2 masks in the ADB's (automatic drop box) are actually individually fired when you pull the mask down... you have heard ';Pull the mask down firmly before placing it over your nose and mouth'; This is because when you pull down on it you activate the valve that initiates the chemical reaction and supplies about 15-20 minutes of o2 for your personal mask.. it does NOT come from a tank in the bottom of the airplane.





Cockpit crews DO receive their o2 from a bottle which is usually in the cockpit. The F/a's also have portable bottles that they can plug on a full face mask and move around the cabin and fight a fire, or the regular mask as needed. There is also supplemental o2 for passengers that require it.. but that must be requested prior to the flight (because the airlines don't want you taking your o2 bottle on board.





o2 bottles in the cargo area can be anything from aircraft related systems, to bottles being sent comail (company mail) that being you have an airplane in West Somewhere and it needs o2 which cannot be readily serviced, you send a bottle out on the next flight to fix it... or bring one back, or just plain cargo... and then you get into the regulations about bottles, and the requirements of how they may be safely and legally shipped on board a passenger carrying aircraft. Just because it's on the plane doesn't mean it was done corretly.. you may recall on the same subject that it was ValuJet 592 that crashed in Florida because some o2 generators were improperly marked and shipped and they ignited in the cargo hold of the DC-9. It is an exothermic reaction and those things can get 500 degrees hot... and the started popping off the others AND fed the fire with o2... small wonder the plane burned up.





o2 on Pax aircraft cargo or cabin is specifically regulated and serious business, you don't just throw on divers tanks and go to the bahamas, you must comply with the FAR's or someone is going to explain to the FAA (assuming they survive)
ludwig 3 is somewhat correct.. however every Boeing model aircraft DOES have a ';CREW'; O2 bottle in the forward cargo bin to the left hand side. the Airbus A330 and above have there's in the E/E bay under the cockpit. they begin at 1800-1900 psi. I have replaced many of them due to the fact that crews use them quite often. they must be at 1000 psi minimal dispatch for overwater operations. the smaller O2 bottles inside the aricraft cabin are for emergency use by flight attendants for passengers that might become ill or have a difficult time breathing. not for fighting fires. . in the event of a fire there is a bag called a PBE that they put on. for the drop down emergency masks there is an oxygen generator which provides just enough per row (one in every row) for a temporary 20 to 30 minute landing so ludwig you are somewhat correct but very far off if your arrogant assumption
I don't fly the 747, but it may be a tank that is used for the crew oxygen masks. Most passenger oxygen masks use oxygen generators, which are self contained. That way, no central tank is required. Not so for crew oxygen. The pilots might need it for a longer period than the passengers, for instance, when there is smoke in the cockpit.
Don`t know how many of you remember the now defunct Valu-jet airlines crash in the everglades of Florida. Those canisters were the blame for that crash, no one survived. I believe it was a DC-9 and happened around the 1980`s.





It turned out I believe that the tanks got loose and exploded, but maybe someone can clarify this further.
those little tubes and masks that drop down in case of loss of cabin pressure; they have to get oxygen from a tank stored somewhere; it makes sense to have the tank out of sight in cargo
to supply the oxygen masks in the passenger cabin.


Passenger Oxygen may be chemical supplied OR supplied by an oxygen tank,





Six years Interior Installer 777. We had either system depending on customer.
Older 747's have a very significant oxygen tank just behind the forward cargo door that is used to provide oxygen to passengers in case of depressurization.
They are most likely for if the life support systems give out, they will be able to breathe that oxygen through masks
Would you rather they were kept in the main cabin where, if they blow, they will instantly kill everyone in the cabin?