As far as I know, you are free to make one for your own personal enjoyment, but if it is going to be used for a 'business' use it will have to be tested and certified.
Adam,
That is kind of what I figured, but what testing and what certificates. This is the golden question that I seem to be hitting a brick wall trying to find an answer to.
Who would govern the design of one of these things. If, as a hypothetical, I built a safe and sound machine, which worked perfectly, and a firework display company then wanted to use these units in a 'commercial' environment, who they hell do I approach to get these things tested and certified. Whose jurisdiction do they come under?
Bone