According to www.dictionary.com:
1. A colorless, odorless, tasteless, gaseous mixture, mainly nitrogen
(approximately 78 percent) and oxygen (approximately 21 percent) with
lesser amounts of argon, carbon dioxide, hydrogen, neon, helium, and
2. This mixture with varying amounts of moisture and particulate
matter, enveloping the earth; the atmosphere.
So it does appear that, from definition 2, David M is correct. However,
according to definition 1, Duane is correct.
So you are both correct! Peace!