Exploding Balloons
- Page ID
- 128812
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Required Training |
Required PPE |
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UC Lab Safety Fundamentals |
Flame-resistant lab coat, safety glasses/goggles, hearing protection, nitrile gloves |
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Performers Required: 1 (2 recommended) |
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Equipment |
Chemicals |
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Latex balloons |
Propane (C3H8), with regulator and tubing installed |
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String |
Hydrogen (H2), with regulator and tubing installed |
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Weighted objects to anchor balloons |
Oxygen (O2), with regulator and tubing installed |
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Tissue fixed to a 1-meter stick/pole |
Ethanol (EtOH), 95% |
Procedure:
1.) Fill the balloons from the gas cylinders with the appropriate gases. This includes pure propane, pure hydrogen, and pure hydrogen and oxygen for a 2:1 mixture. Tie the gas balloons off and attach the strings to both the balloons and the weighted anchors. The H2 and O2 for the mixture should not be tied, but should be reversibly-sealed to prevent leaking. These should never be combined before transport. Label the top of each balloon with a sharpie marker.
2.) Position the balloons and their anchors at least 10 feet from the audience.
3.) Ensure you are wearing hearing protection and that the audience has been warned to cover their ears before proceeding. Make sure you are standing upwind of the balloon. Light the ethanol-soaked tissue on the end of the pole, and place it next to the balloon so that the flame touches the balloon, not the tissue. It will pop (air), ignite (H2 and C3H8), or explode (H2/O2) after a few seconds. The H2/O2 will release a shockwave.
Clean-up: Make sure to clean up all of the pieces of latex and string.
Hazards: The H2, C3H8, and H2/O2 balloons produce heat, fire, and a loud noise when ignited. Hazards include thermal burns from the fire and hearing damage from the explosion. When transporting H2, C3H8, and H2/O2 balloons, take care to keep them away from ignition sources and each other, if moving multiple balloons. They should never be grouped into a bag for transportation, as the build-up of static electricity could cause them to ignite. Never bring a H2/O2 balloon into a confined space such as an elevator, as an accidental explosion could cause deafness and great personal injury. H2/O2 balloons cannot be transported in vehicles for legal reasons, and may only be used for outdoor demonstrations. However, transporting H2 and O2 balloons together is fine, so do not combine them until transportation to the site is complete.
Principle: The air balloon doesn’t explode because the components have not reached the upper flammable limit. The flammable gases in the balloons combust into water vapor (and CO2 with C3H8 fuel) when ignited. The C3H8 balloon releases the most energy, but it has the lowest power because the combustion proceeds slowly. The H2 balloon releases approximately 1/3rd of the energy, but it burns much faster and therefore produces much more power. The H2/O2 balloon releases the same energy as the H2 balloon, but with significantly more power (creating a shock wave); the H2 does not need to diffuse into the air to mix with oxygen, the combustion occurs with much greater speed.
Notes: When making mixed H2/O2 balloons, first fill the balloon one third with oxygen, and then fill it the rest of the way with hydrogen, stopping shortly after it becomes positively buoyant. This is still a very oxygen-rich mixture, but it limits the concussive force of the explosion. The mixed balloons should not exceed 6-8” in diameter, and must never be ignited indoors. Never make a mixed CH4/O2 balloon – the power output is too large (~3 times that of a H2/O2 balloon), making it unsafe for performance even when outdoors. Methane does not work well as a balloon do to it’s variable results. We no longer use helium due to finite resources and its need in medical devices and scientific experiments.