Learning about a Hydrogen Torch could be your first step to understanding HHO or hydrogen on demand generation.
Here's what I think I understand about torches that are powered by hydrogen. First you assemble an electrolyzer or hydrogen generator that will allow you to produce hydrogen. It could be solar powered, battery, or through a combination of certain metals, such as barium, aluminum, etc., and electrolytes, and/or bacteria.
Watch a YouTube Video on how to build a Torch
From that assembly you can then attach a torch of any size you want depending on where or what you want to use it on. If you're an artist you can have the mini or pencil torch which is a portable one for jewelry making, or bigger ones for cutting iron/steel and stones.
The National Model 3H Hydrogen Hand Torch is specially designed for use with Hydrogen and Oxygen. The 3H comes with a 7" stainless steel elbow and has 3/8-24, "A" size, threaded welding hose connections.
Max 150 watts or 12 amp 12 volt for as much gas as 1.5 liter per minute! The 1.5 LPM hho minitorch is a perfect demo or experimental kit.
Source of Pictures: Brown's Gas
The advantage with a hydrogen powered torch is that it is claimed to be much more powerful than ordinary gas and with the kind of generators used, it is environmentally friendly since the only exhaust is water and is cost efficient since it is also generated from WATER.
A Hydrogen powered torch also provides us with a concrete example of how HHO or hydrogen on demand works and is based upon the same theory on gas combustion to power up engines.