Per ATF (Alcohol Tobacco Firearms and Explosives) for Class B fireworks they need to be stored in a fully enclosed container with no windows. Sides, doors need to be a minimum lined with 3/4 plywood. If it was an elevated floor such as a trail believe that was 1". There was something about the locking system also. Roof can't remember what the requirements are but it's lite compared to the sides and floors as they want the blast to go up and not out.
When we shot we had 2 semi trailers that we lined. Over the years an ATF inspector did come and inspect the trailers.
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Doug ·