Rudeboy, NITROMETHANE is an explosive, and is hazardous when it's vapors mix with air or it's container is exposed to shock, such as tipping over, being struck, etc.

You mention the storage of gasoline. Typically, gasoline is stored in 1 or 5 gallon cans. In order to save your few bucks a gallon on model airplane fuel, you'll need to buy 50 gallon drums of nitromethane. Cool... Keep it in YOUR garage, and not within a block of MY house.

As far as knowing what is in your fuel, there are a few manufacturers of glow fuel that give you a very good and accurate list of the contents of their fuel, and often the quality and type of ingredients.

Do your homework before suggesting to someone that they store hazardous chemicals in their garage.