Pat,
When does the law ever state what you are looking for? I got pulled over this morning for "Jack Rabbitting" off the light. Try to find that law written somewhere? I am having some degree of difficulty finding that one... Law is written so that only the judge, an officer enforcing it, and a high priced lawyer can figure it out. They interpret the law and that is what you get.

The key to "is it legal"? Well, the answer seems to be yes. What you have is "no intent to breathe, inhale, or drink" and "(3) Except as provided in subsection (4)" which are subsections F and G. Your Nitrous is used for combustion propulsion and it contains not less than 100 parts per million of sulfur dioxide. Seems to me that this is within the law and that makes it legal. Now I am not too sure how the officer will like you pointing this out, but that does seem to be the law. Now when you get pulled over, see how things go. Be nice and hopefully you won't have any issues. Now if things are going badly, well, might as well add some "NOS" to the fire....