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Hydrogen is probably not as unsafe as the general population might think it is, but it find it bizarre just how much the article downplays the flammability issu

Hydrogen is probably not as unsafe as the general population might think it is, but it find it bizarre just how much the article downplays the flammability issue. For example: > Fun fact: pure hydrogen doesn’t burn. It needs an oxidizer—like the oxygen in air. Airships literally float in that oxidizier!

contravariant 5y ago
Yeah it kind of defeats the point when your definition of 'doesn't burn' covers every single substance.
- dragontamer 5y ago
  Except Li-ion batteries, which burn with their own oxidizer.
  - hobs 5y ago
    Well there's plenty of monoprops that supply their own oxidizer, and oh boy are they absolutely dangerous as hell. https://en.wikipedia.org/wiki/Monopropellant https://en.wikipedia.org/wiki/Monopropellant
  - yellow_lead 5y ago
    And rocket fuel? Technically
    - dragontamer 5y ago
      Rocket fuel is more of a "pre-mixed with oxidizier" sorta thing. Although I am enjoying the side discussion about monopropellants.
    - gpm 5y ago
      Most modern rockets are liquid and mix the fuel and oxidizer only at the point of combustion, burning H2/O2, Kerosene/O2 or more recently CH4/O2. Mono-propellant, and solid (not hybrid) rocket fuel fits the description though
      - crazydoggers 5y ago
        > Mono-propellant, and solid (not hybrid) rocket fuel fits the description though Decomposition doesn’t count as “burning” which means combustion. Fusion and fission release energy as well, but I don’t think anyone calls fusion “burning” hydrogen.
        gpm 5y ago
        Generally I don't think this type of language debate is useful, we aren't debating what is happening, just what to call it, and that's pretty boring. If you want to call it not burning, ok, be my guest. Hopefully my answer is still an interesting point about the kinds of violent chemical reactions that exist and could make a substance dangerous to work with in an environment without (outside, in the case of solid rocket fuel) oxidizing agents. I'll make an exception and reply about the language in this case because I there's a broader point I want to make: English isn't a language defined based of "X happens if chemical reactions Y happens behind the scenes", because we didn't even know about chemical reaction Y when English was invented. Moreover if you tried to define it as oxidation you'd fail, rust isn't burning, meanwhile (non-oxidizing) chemical burns, sunburns, etc all exist because they were just analogous enough to the concept of fire. If people knew about some chemical that decomposes into plasma in the 1600s, they definitely called it burning even if there was no oxidation. Meanwhile people definitely refer to fusion as "burning", e.g. see this stackexchange question with lots of links to wikipedia and the like which refer to different kinds of fusion as burning [1] or ctrl-f burning in this wikipedia article [2] (which is linked from [1]). [1] https://astronomy.stackexchange.com/questions/43907/hydrogen-burning-vs-hydrogen-fusing https://astronomy.stackexchange.com/questions/43907/hydrogen... [2] https://en.wikipedia.org/wiki/Stellar_nucleosynthesis https://en.wikipedia.org/wiki/Stellar_nucleosynthesis
        crazydoggers 5y ago
        I don’t really take this as a language debate though. It clearly is about the fact that people don’t understand what an oxidizer is at a chemical level. Someone who says the following isn’t just using language inaccurately, it actually shows a fundamental misunderstanding of combustion: > pure hydrogen doesn’t burn. It needs an oxidizer—like the oxygen in air. That statement, no matter how you take it, leaves an assumption that other gases might burn like hydrogen without oxygen, which is again a fundamental misunderstanding of chemistry. In addition calling something “self oxidizing” doesn’t make sense. There are always mixtures of fuel and oxidizers… whether those are gas and fuel, solid and fuel, mixed in gunpowder form, mixed as gasoline and air in a carburetor, etc. So if I supply you a balloon with the proper stoichiometric ratio of gasoline and air, is that “self-oxidizing”? If so then everything is self oxidizing. And while I would agree that people do refer to fusion as “burning” I actually think this is a again a prime example of people not understanding the underlying physics. Most people don’t understand how fusion works, so calling it “burning” is a lazy way to conceptualize what the sun is doing. Scientists will sometimes use “burning hydrogen” when talking about nucleosynthesis, but they assume the audience of other scientists understand the difference between combustion and fusion. When articles like the original post are talking to the layperson in this manner however, it does nothing but lead to more scientific illiteracy. A perfect example is one of the above comments: > There are rumours that because of this fact, that the Hindenburg disaster was not from natural causes. If we don’t communicate science effectively then we end up with conspiracies and pseudoscience. Words are tools. They should be used wisely.
- gpm 5y ago
  Self oxidizing mixtures exist. Gun powder is probably the classic example. Monopropellants, that aren't mixtures, exist and "burn" too, high concentration H2O2 for instance.
  - toomanybeersies 5y ago
    T-Stoff/High-Test Peroxide doesn't actually burn, but rather decomposes into water and oxygen.
  - rbanffy 5y ago
    They can still burn in the presence of an oxidiser. They don't need it, but that won't stop them from burning, or blowing up, or doing whatever they want to do, as monopropellants are really (no pun intended) impulsive.
  - crazydoggers 5y ago
    Gunpowder still requires an oxidizer, it just happens to be mixed in. The potassium nitrate is the oxidizer, KN03, whereas the sulphur and charcoal are the fuels that burn. Pretty much any combustion requires a molecule with oxygen to accept the electrons: exceptions exist with halogens like chlorine… but these are still called “oxidizers” So saying hydrogen doesn’t burn without an oxidizer still makes little sense. Hydrogen will combust with either oxygen or chlorine for example, both oxidizers. Without those then nothing happens because nothing can combust without an oxidizer… You may just not realize the oxidizer is mixed with the fuel.
    - jandrewrogers 5y ago
      Technically speaking, sulfur is an oxidizer in gunpowder, not fuel. Sulfur is even in the same elemental group as oxygen. Sulfur is commonly used as an oxidizer for metal fuels. In the case of gunpowder, that would be the potassium in potassium nitrate.
      - crazydoggers 5y ago
        That’s not correct. (Sulfur can be an oxidizer in some reactions as you mention, but not in gunpowder where it acts as the fuel) https://www.wikipedia.org/wiki/Gunpowder#Components https://www.wikipedia.org/wiki/Gunpowder#Components Potassium nitrate is the most important ingredient in terms of both bulk and function because the combustion process releases oxygen from the potassium nitrate, promoting the rapid burning of the other ingredients Sulfur's main role in gunpowder is to decrease the ignition temperature. A sample reaction for sulfur-free gunpowder would be: 6 KNO3 + C7H4O → 3 K2CO3 + 4 CO2 + 2 H2O + 3 N2
JulianMorrison 5y ago
But they only burn easily at the interface. The trick would be to control fire there - keep them from mixing, keep the flame, if one were to start, from enlarging the hole.
- minikites 5y ago
  Good point. I remember a science demonstration where lighting a balloon filled with a mixture of hydrogen and oxygen caused a much more violent eruption compared to a balloon of pure hydrogen.
  - dredmorbius 5y ago
    Both pure hydrogen and a stochiometric hydrogen-oxygen mixture explode (produce a bang, indicating a flame front moving faster than the speed of sound). The stochiometric mixture explodes more violently, true. But again, both explode. Periodic Videos, feat. Destin Sandlin: https://youtube.com/watch?v=qOTgeeTB_kA https://youtube.com/watch?v=qOTgeeTB_kA
- GauntletWizard 5y ago
  Not only control where the fire is, but do so with materials light enough for an airship. It's a hard problem.
  - JulianMorrison 5y ago
    Not necessarily. Remember, you only need to control the interface. A bag, not a wall.
R0b0t1 5y ago
The burning plume escapes upward. It's probably safer than aviation fuel.
- varjag 5y ago
  Right, seen that in Hindenburg footage.
  - R0b0t1 5y ago
    The Hindenburg was covered in aluminum paint.
    - varjag 5y ago
      Aluminium must be really exotic material in airspace applications? Also: The truth is that the dope used on the Hindenburg was specifically chosen for its low flammability, and the composition of the dope had almost nothing in common with the formula used to make rocket fuel. https://www.airships.net/hindenburg-paint/ https://www.airships.net/hindenburg-paint/
      - R0b0t1 5y ago
        You're trying to be witty but the crashing airframe of a lighter than air craft is very likely to do less damage mainly due to its slower speed and the fact most flammable material escapes upwards. Have you thought through this at all?
        varjag 5y ago
        It is well established that a burning dirigible incident is not very survivable. I'm not sure why am the one being unreasonable here. I could understand if hydrogen balloons were never tried before tech, but you're just gaslighting now.
        dredmorbius 5y ago
aww_dang 5y ago
https://en.wikipedia.org/wiki/Pomeroy_bullet https://en.wikipedia.org/wiki/Pomeroy_bullet The British anti-zeppelin forces researched this problem and were unable to come up with a method of reliably igniting the hydrogen gas.
- Retric 5y ago
  Crashing aircraft into them was quite reliable, it just wasn’t cheap.
kurthr 5y ago
Even that wouldn't be such a big issue, if the flammability limit of hydrogen is from 4% to 74% in air (~20x). For comparison gasoline vapor is 1.4% to 7.6% (~5x) In an open space that's not so bad since the flammable material literally floats away (while gasoline vapor settles), but it's still an issue in any contained area.
- kurthr 5y ago
  oops that was supposed to be a wouldn't/wasn't construction. The is doesn't make sense.
TinyBig 5y ago
"Floating in oxidizer" doesn't matter - airships are under such low pressure that leaks are too slow to maintain a flame front. I researched this quite a bit for the Army back in the day, even worked with a vendor who fired 50 caliber tracer rounds through an airship to try to get it to catch on fire, and it did not.
- MichaelZuo 5y ago
  There are rumours that because of this fact, that the Hindenburg disaster was not from natural causes.
  - solarkraft 5y ago
    Okay, what’s the alternative scenario and how do we ensure that doesn’t happen?
    - elliottkember 5y ago
      Rips along the seams of the fabric siding causing large surface areas of hydrogen to be mixed, I think?
    - m4rtink 5y ago
      IIRC something about the pain used on the aerodynamic outer shell (the gas cells inside were separate gas tight balloons made from processed cattle stomach tissue (!)). This paint apparently turned out to be highly flammable and/or explosive and could be activated by dischrges of static electricity.
    - ant6n 5y ago
      I think there was static discharge involved, and thermite paint. And of course a giant bag filled with hydrogen, surrounded by oxygen.
      - max-ibel 5y ago
        Iirc there is a great YouTube video with Bill Hammack about this. Highly recommended. https://youtu.be/ixxXhZVFXxQ https://youtu.be/ixxXhZVFXxQ He also wrote a book.

contravariant 5y ago

Yeah it kind of defeats the point when your definition of 'doesn't burn' covers every single substance.

dragontamer 5y ago
Except Li-ion batteries, which burn with their own oxidizer.
- hobs 5y ago
  Well there's plenty of monoprops that supply their own oxidizer, and oh boy are they absolutely dangerous as hell. https://en.wikipedia.org/wiki/Monopropellant https://en.wikipedia.org/wiki/Monopropellant
- yellow_lead 5y ago
  And rocket fuel? Technically
  - dragontamer 5y ago
    Rocket fuel is more of a "pre-mixed with oxidizier" sorta thing. Although I am enjoying the side discussion about monopropellants.
  - gpm 5y ago
    Most modern rockets are liquid and mix the fuel and oxidizer only at the point of combustion, burning H2/O2, Kerosene/O2 or more recently CH4/O2. Mono-propellant, and solid (not hybrid) rocket fuel fits the description though
    - crazydoggers 5y ago
      > Mono-propellant, and solid (not hybrid) rocket fuel fits the description though Decomposition doesn’t count as “burning” which means combustion. Fusion and fission release energy as well, but I don’t think anyone calls fusion “burning” hydrogen.
      - gpm 5y ago
        Generally I don't think this type of language debate is useful, we aren't debating what is happening, just what to call it, and that's pretty boring. If you want to call it not burning, ok, be my guest. Hopefully my answer is still an interesting point about the kinds of violent chemical reactions that exist and could make a substance dangerous to work with in an environment without (outside, in the case of solid rocket fuel) oxidizing agents. I'll make an exception and reply about the language in this case because I there's a broader point I want to make: English isn't a language defined based of "X happens if chemical reactions Y happens behind the scenes", because we didn't even know about chemical reaction Y when English was invented. Moreover if you tried to define it as oxidation you'd fail, rust isn't burning, meanwhile (non-oxidizing) chemical burns, sunburns, etc all exist because they were just analogous enough to the concept of fire. If people knew about some chemical that decomposes into plasma in the 1600s, they definitely called it burning even if there was no oxidation. Meanwhile people definitely refer to fusion as "burning", e.g. see this stackexchange question with lots of links to wikipedia and the like which refer to different kinds of fusion as burning [1] or ctrl-f burning in this wikipedia article [2] (which is linked from [1]). [1] https://astronomy.stackexchange.com/questions/43907/hydrogen-burning-vs-hydrogen-fusing https://astronomy.stackexchange.com/questions/43907/hydrogen... [2] https://en.wikipedia.org/wiki/Stellar_nucleosynthesis https://en.wikipedia.org/wiki/Stellar_nucleosynthesis
        crazydoggers 5y ago
        I don’t really take this as a language debate though. It clearly is about the fact that people don’t understand what an oxidizer is at a chemical level. Someone who says the following isn’t just using language inaccurately, it actually shows a fundamental misunderstanding of combustion: > pure hydrogen doesn’t burn. It needs an oxidizer—like the oxygen in air. That statement, no matter how you take it, leaves an assumption that other gases might burn like hydrogen without oxygen, which is again a fundamental misunderstanding of chemistry. In addition calling something “self oxidizing” doesn’t make sense. There are always mixtures of fuel and oxidizers… whether those are gas and fuel, solid and fuel, mixed in gunpowder form, mixed as gasoline and air in a carburetor, etc. So if I supply you a balloon with the proper stoichiometric ratio of gasoline and air, is that “self-oxidizing”? If so then everything is self oxidizing. And while I would agree that people do refer to fusion as “burning” I actually think this is a again a prime example of people not understanding the underlying physics. Most people don’t understand how fusion works, so calling it “burning” is a lazy way to conceptualize what the sun is doing. Scientists will sometimes use “burning hydrogen” when talking about nucleosynthesis, but they assume the audience of other scientists understand the difference between combustion and fusion. When articles like the original post are talking to the layperson in this manner however, it does nothing but lead to more scientific illiteracy. A perfect example is one of the above comments: > There are rumours that because of this fact, that the Hindenburg disaster was not from natural causes. If we don’t communicate science effectively then we end up with conspiracies and pseudoscience. Words are tools. They should be used wisely.
gpm 5y ago
Self oxidizing mixtures exist. Gun powder is probably the classic example. Monopropellants, that aren't mixtures, exist and "burn" too, high concentration H2O2 for instance.
- toomanybeersies 5y ago
  T-Stoff/High-Test Peroxide doesn't actually burn, but rather decomposes into water and oxygen.
- rbanffy 5y ago
  They can still burn in the presence of an oxidiser. They don't need it, but that won't stop them from burning, or blowing up, or doing whatever they want to do, as monopropellants are really (no pun intended) impulsive.
- crazydoggers 5y ago
  Gunpowder still requires an oxidizer, it just happens to be mixed in. The potassium nitrate is the oxidizer, KN03, whereas the sulphur and charcoal are the fuels that burn. Pretty much any combustion requires a molecule with oxygen to accept the electrons: exceptions exist with halogens like chlorine… but these are still called “oxidizers” So saying hydrogen doesn’t burn without an oxidizer still makes little sense. Hydrogen will combust with either oxygen or chlorine for example, both oxidizers. Without those then nothing happens because nothing can combust without an oxidizer… You may just not realize the oxidizer is mixed with the fuel.
  - jandrewrogers 5y ago
    Technically speaking, sulfur is an oxidizer in gunpowder, not fuel. Sulfur is even in the same elemental group as oxygen. Sulfur is commonly used as an oxidizer for metal fuels. In the case of gunpowder, that would be the potassium in potassium nitrate.
    - crazydoggers 5y ago
      That’s not correct. (Sulfur can be an oxidizer in some reactions as you mention, but not in gunpowder where it acts as the fuel) https://www.wikipedia.org/wiki/Gunpowder#Components https://www.wikipedia.org/wiki/Gunpowder#Components Potassium nitrate is the most important ingredient in terms of both bulk and function because the combustion process releases oxygen from the potassium nitrate, promoting the rapid burning of the other ingredients Sulfur's main role in gunpowder is to decrease the ignition temperature. A sample reaction for sulfur-free gunpowder would be: 6 KNO3 + C7H4O → 3 K2CO3 + 4 CO2 + 2 H2O + 3 N2

JulianMorrison 5y ago

But they only burn easily at the interface. The trick would be to control fire there - keep them from mixing, keep the flame, if one were to start, from enlarging the hole.

minikites 5y ago
Good point. I remember a science demonstration where lighting a balloon filled with a mixture of hydrogen and oxygen caused a much more violent eruption compared to a balloon of pure hydrogen.
- dredmorbius 5y ago
  Both pure hydrogen and a stochiometric hydrogen-oxygen mixture explode (produce a bang, indicating a flame front moving faster than the speed of sound). The stochiometric mixture explodes more violently, true. But again, both explode. Periodic Videos, feat. Destin Sandlin: https://youtube.com/watch?v=qOTgeeTB_kA https://youtube.com/watch?v=qOTgeeTB_kA
GauntletWizard 5y ago
Not only control where the fire is, but do so with materials light enough for an airship. It's a hard problem.
- JulianMorrison 5y ago
  Not necessarily. Remember, you only need to control the interface. A bag, not a wall.

R0b0t1 5y ago

The burning plume escapes upward. It's probably safer than aviation fuel.

varjag 5y ago
Right, seen that in Hindenburg footage.
- R0b0t1 5y ago
  The Hindenburg was covered in aluminum paint.
  - varjag 5y ago
    Aluminium must be really exotic material in airspace applications? Also: The truth is that the dope used on the Hindenburg was specifically chosen for its low flammability, and the composition of the dope had almost nothing in common with the formula used to make rocket fuel. https://www.airships.net/hindenburg-paint/ https://www.airships.net/hindenburg-paint/
    - R0b0t1 5y ago
      You're trying to be witty but the crashing airframe of a lighter than air craft is very likely to do less damage mainly due to its slower speed and the fact most flammable material escapes upwards. Have you thought through this at all?
      - varjag 5y ago
        It is well established that a burning dirigible incident is not very survivable. I'm not sure why am the one being unreasonable here. I could understand if hydrogen balloons were never tried before tech, but you're just gaslighting now.
        dredmorbius 5y ago

aww_dang 5y ago

https://en.wikipedia.org/wiki/Pomeroy_bullet https://en.wikipedia.org/wiki/Pomeroy_bullet The British anti-zeppelin forces researched this problem and were unable to come up with a method of reliably igniting the hydrogen gas.

Retric 5y ago
Crashing aircraft into them was quite reliable, it just wasn’t cheap.

kurthr 5y ago

Even that wouldn't be such a big issue, if the flammability limit of hydrogen is from 4% to 74% in air (~20x). For comparison gasoline vapor is 1.4% to 7.6% (~5x) In an open space that's not so bad since the flammable material literally floats away (while gasoline vapor settles), but it's still an issue in any contained area.

kurthr 5y ago
oops that was supposed to be a wouldn't/wasn't construction. The is doesn't make sense.

TinyBig 5y ago

"Floating in oxidizer" doesn't matter - airships are under such low pressure that leaks are too slow to maintain a flame front. I researched this quite a bit for the Army back in the day, even worked with a vendor who fired 50 caliber tracer rounds through an airship to try to get it to catch on fire, and it did not.

MichaelZuo 5y ago
There are rumours that because of this fact, that the Hindenburg disaster was not from natural causes.
- solarkraft 5y ago
  Okay, what’s the alternative scenario and how do we ensure that doesn’t happen?
  - elliottkember 5y ago
    Rips along the seams of the fabric siding causing large surface areas of hydrogen to be mixed, I think?
  - m4rtink 5y ago
    IIRC something about the pain used on the aerodynamic outer shell (the gas cells inside were separate gas tight balloons made from processed cattle stomach tissue (!)). This paint apparently turned out to be highly flammable and/or explosive and could be activated by dischrges of static electricity.
  - ant6n 5y ago
    I think there was static discharge involved, and thermite paint. And of course a giant bag filled with hydrogen, surrounded by oxygen.
    - max-ibel 5y ago
      Iirc there is a great YouTube video with Bill Hammack about this. Highly recommended. https://youtu.be/ixxXhZVFXxQ https://youtu.be/ixxXhZVFXxQ He also wrote a book.