Nov 12 2011

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Hydrogen Balloon Test Complete

Friday the 11th we performed an experiment with hydrogen to verify that it is possible to handle safely, and that even if it does explode there is relatively little danger.

In this experiment we took small latex balloons and filled them outside with hydrogen. We had a short pipe extending from the regulator attached to the hydrogen tank. We first blew some hydrogen through the pipe to make sure there was no air in it. Then we attached the completely deflated balloon and slowly filled it up. Then we tied a knot in the inflated balloon and tied a weighted string to it. After that, we brought it inside.

We filled the balloon outside because we didn’t want any hydrogen leaking out and potentially accumulating on the ceiling, where it would just stick around as a pocket of mixed flammable gas, which is dangerous.

We also made sure to make the balloon filled completely with hydrogen and no other gases. This is important, as a mixture of air with the hydrogen would facilitate a much faster reaction; a real explosion.

After bringing the filled and sealed balloon inside, we set it down, focused a very bright spotlight on it (the high speed camera requires a lot of light), started the high speed camera, and then touched the balloon with a kerosene-soaked rag on a pole.  This ignited the hydrogen, which burned rapidly. Here’s the first video:

As you can see, there’s a very rapid fire, but the noise is just as loud as a regular balloon, and though we are standing only a few feet away there is no large blast and we only barely felt the heat. We performed the same test a second time with a different framerate and a person in the shot for perspective and context:

There are some important notes from these tests.

  1. Hydrogen is VERY flammable, but it can be safely handled.
  2. The reaction with hydrogen involves heat, hydrogen, and oxygen. Without all three, it’s very boring.
  3. The hydrogen balloon alone is very easy to handle and if it pops the hydrogen will mix into the atmosphere quickly and rise, so it should be done outside, but nothing bad will happen if you handle hydrogen outside without any sources of spark or flame nearby.
  4. Even a spark needs to be extremely close to the hydrogen and spark across both hydrogen and oxygen to start the reaction. A flame or spark a few feet away will not cause an explosion, but don’t press your luck.
  5. Finally, with a pure hydrogen balloon, if there is a heat source, then the fire will consume the hydrogen from the outside in as the air mixes with the hydrogen. It’s a fast fireball, not an explosion outwards. That’s why we were so comfortable being close to the balloon.
  6. BIG IMPORTANT NOTE: Do NOT mix hydrogen with air and then ignite it. That will cause an extremely rapid reaction as all the hydrogen reacts with the oxygen at once and you get an explosion. A pure hydrogen balloon is MUCH safer than one mixed with air. Better yet, just don’t ignite it. We did the experiment so you don’t have to.
  7. BIGGER IMPORTANT NOTE: We do NOT assume responsibility or liability for anything you do based on what you’ve read on this site or in any communication with us. While we believe our advice is sound and we have taken precautions to protect ourselves (we didn’t show the tests outside in the dark, we didn’t show the fire extinguisher nearby, and all the other small tests we did to get comfortable enough to make those videos), we don’t know how you will decide to do something stupid and hurt yourself. Hydrogen CAN be very dangerous if not handled properly.

One final bit. We did this experiment because we know a lot of people have some gut reactions to the thought of using hydrogen to fill a balloon around children. We wanted to show that it won’t cause an explosion if done right, and there shouldn’t be any reason for this to go wrong. Even if it did, it probably wouldn’t be a big deal as these videos show. Still, Murphy lurks around every corner, so we strongly recommend that kids stay at a respectable distance during the filling until the balloon is launched, and that you choose a place to fill and launch that is not near any sources of flame or sparks or power lines.  Hydrogen is a reasonable and cheap gas to use for this project and we hope these videos convince you that it can be done in the presence of youngsters.

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