Wiktionary
zero air
n. purified atmospheric air to contain less than 0.1 ppm total hydrocarbons.
Wikipedia
Zero air
<!-- This long comment was added to the page to prevent it being listed on Special:Shortpages. It and the accompanying monitoring template were generated via Template:Longcomment. Please do not remove the monitor template without removing the comment as well.
Usage examples of "zero air".
Some eighty-below-zero air hit my nose, and that's when I got this pleasant little frostbite to add to the bump I acquired during the crash of my rocket.