4 ms·

Does anyone have any idea why CO2 levels would spike so high when a plane takes off?

pstrateman 4y ago
When planes take off there's often a strong smell of exhaust. Presumably the external air mix is just full of exhaust before they're at speed.
- pornel 4y ago
  Or perhaps external air intake is closed/limited because of the smell.
akira2501 4y ago
I'm not exactly sure, but during take off the "packs" are typically disabled. This removes air conditioning and probably lowers the amount of air that would be circulating when they are enabled.
- sokoloff 4y ago
  The air cycle machine (“packs”) are turned off if maximum power is needed (as their use requires bleed air, which takes power from the engine).
  - mleonhard 4y ago
    The author's DEN-LHR flight was on a Boeing 787 aircraft, which use electrically-powered air compressors [0]. They do not draw air from the engine. 787 maintain internal air pressure equivalent to 6,000 feet of elevation. All other commercial aircraft maintain 8,000 feet air pressure. I think most of my discomfort from long flights is due to altitude sickness. The only time I have slept on a long flight and awakened refreshed was on a 787. Jet engines use a neuro-toxic lubricant. Occasionally, some of this enters the cabin through the compressed air feed and poisons the passengers [1]. 787 passengers don't have this risk because the planes don't draw air from engines. [0] https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Interior https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Interior [1] https://pubmed.ncbi.nlm.nih.gov/24713335/ https://pubmed.ncbi.nlm.nih.gov/24713335/
    - Baeocystin 4y ago
      I sometimes take commuter flights between San Jose and San Diego, which are almost always Southwest 737's, and I've only seen 6,000 feet on the barometer when I've checked, probably about half a dozen times out of curiosity. FWIW.
    - MichaelZuo 4y ago
      So then what explains the mysterious lack of air circulation during takeoffs on the 787?
      - pifm_guy 4y ago
        Probably just the pilot didn't flick the switch for it while he was having his coffee break while the passengers were boarding. I'd bet if you can get a few popular newspapers to write articles about this with scary headlines ('Airline nearly suffocates passengers - and doesn't even apologize!'), then airlines will remind pilots not to do that...
        MichaelZuo 4y ago
        But for half an hour? That seems like quite a long time to ignore an obvious item on the flight checklist.
    - Reason077 4y ago
      > "I think most of my discomfort from long flights is due to altitude sickness." Seems unlikely. Actual altitude sickness is generally considered to occur only above 8000 ft, and above 10000 ft is where the real risk begins. Symptoms generally don't appear until 12-24 hours after climbing to altitude. Also, risk of altitude sickness increases with physical exertion, and you're probably not doing much of that on a plane!
    - pistoriusp 4y ago
      Maybe stress related?
etrautmann 4y ago
Almost certainly the effect of combustion of jet fuel - which is not a good proxy for Covid risk of course. This article seems to conflate those two a bit, though the data is interesting
- jeffbee 4y ago
  Bleed air is taken from the compressors before the combustion section, so it's probably not CO2 from combustion. If it was, it would also be humid and stink of kerosene, which it's not (cabin air is notoriously dry except on the 787) and doesn't (fuel smells in cabins have other causes). CO2 rises in the cabin during taxi because the bleed air system is not effective while the aircraft is moving slowly. This is another good feature of the 787: cabin air conditioning works adequately even with the aircraft at rest.
hardaker 4y ago
note that probably after hackernews caught the page (before all the data was in) I added a link by Boeing about this and what their belief is about CO2 levels at takeoff and in flight.

When planes take off there's often a strong smell of exhaust. Presumably the external air mix is just full of exhaust before they're at speed.

pornel 4y ago
Or perhaps external air intake is closed/limited because of the smell.

akira2501 4y ago

I'm not exactly sure, but during take off the "packs" are typically disabled. This removes air conditioning and probably lowers the amount of air that would be circulating when they are enabled.

sokoloff 4y ago
The air cycle machine (“packs”) are turned off if maximum power is needed (as their use requires bleed air, which takes power from the engine).
- mleonhard 4y ago
  The author's DEN-LHR flight was on a Boeing 787 aircraft, which use electrically-powered air compressors [0]. They do not draw air from the engine. 787 maintain internal air pressure equivalent to 6,000 feet of elevation. All other commercial aircraft maintain 8,000 feet air pressure. I think most of my discomfort from long flights is due to altitude sickness. The only time I have slept on a long flight and awakened refreshed was on a 787. Jet engines use a neuro-toxic lubricant. Occasionally, some of this enters the cabin through the compressed air feed and poisons the passengers [1]. 787 passengers don't have this risk because the planes don't draw air from engines. [0] https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Interior https://en.wikipedia.org/wiki/Boeing_787_Dreamliner#Interior [1] https://pubmed.ncbi.nlm.nih.gov/24713335/ https://pubmed.ncbi.nlm.nih.gov/24713335/
  - Baeocystin 4y ago
    I sometimes take commuter flights between San Jose and San Diego, which are almost always Southwest 737's, and I've only seen 6,000 feet on the barometer when I've checked, probably about half a dozen times out of curiosity. FWIW.
  - MichaelZuo 4y ago
    So then what explains the mysterious lack of air circulation during takeoffs on the 787?
    - pifm_guy 4y ago
      Probably just the pilot didn't flick the switch for it while he was having his coffee break while the passengers were boarding. I'd bet if you can get a few popular newspapers to write articles about this with scary headlines ('Airline nearly suffocates passengers - and doesn't even apologize!'), then airlines will remind pilots not to do that...
      - MichaelZuo 4y ago
        But for half an hour? That seems like quite a long time to ignore an obvious item on the flight checklist.
  - Reason077 4y ago
    > "I think most of my discomfort from long flights is due to altitude sickness." Seems unlikely. Actual altitude sickness is generally considered to occur only above 8000 ft, and above 10000 ft is where the real risk begins. Symptoms generally don't appear until 12-24 hours after climbing to altitude. Also, risk of altitude sickness increases with physical exertion, and you're probably not doing much of that on a plane!
  - pistoriusp 4y ago
    Maybe stress related?

etrautmann 4y ago

Almost certainly the effect of combustion of jet fuel - which is not a good proxy for Covid risk of course. This article seems to conflate those two a bit, though the data is interesting

jeffbee 4y ago
Bleed air is taken from the compressors before the combustion section, so it's probably not CO2 from combustion. If it was, it would also be humid and stink of kerosene, which it's not (cabin air is notoriously dry except on the 787) and doesn't (fuel smells in cabins have other causes). CO2 rises in the cabin during taxi because the bleed air system is not effective while the aircraft is moving slowly. This is another good feature of the 787: cabin air conditioning works adequately even with the aircraft at rest.

hardaker 4y ago

note that probably after hackernews caught the page (before all the data was in) I added a link by Boeing about this and what their belief is about CO2 levels at takeoff and in flight.