"Dog Breath" Flame Effect
 

IMPORTANT:
If you are designing something similar to this effect DO NOT USE THE INFORMATION HERE AS YOUR ONLY SOURCE! I wouldn't. Make no assumptions regarding the materials, components, and their applications as shown. Propane is corrosive to some materials, pressures can become excessive, fire will burn you, things can blow up. This is dangerous, you are responsible for your own safety, do not blame me.
 
Here are a few resources to begin researching. Understand completely what is required and why:

• Burning Man - Creating Dangerous Artwork Safely
• Burning Man - Flame Effects Guidelines
• Pyro Tribe

Installed view - June 16, 2010
 

Twin Tanker Trailer - July 11, 2011
 

Propane boils off from a supply tank by absorbing heat. As the surface of the supply tank cools vapor pressure drops. By adding a second supply tank, and more surface area, vapor pressures can be maintained for a longer period of time. The images above show an expansion to the central carrier to hold a second 20# propane supply tank.