David Martel wrote:

Duane,

Are you starting with a definition of air and then insisting that
everything else are contaminants?

Yep..."air" is the mixutre of gases, the particulate crap ain't...

Air is a mixture of all sorts of stuff.

Yes, N, and O, w/ small amounts of others. I don't have my Handbook of
Chemistry and Physics at hand for precise numbers, but you got the idea
above...

Comes from being a ChE minor, I suppose...