air space

ilmakehä (alternative spelling of)
2005, Paul Foy, "http://www.foxnews.com/wires/2008Aug06/0,4670,UtahMineCollapse,00.html Year after Utah mine collapse, many failures clear," FOXnew.com (retrieved 30 July 2010):

At that point there was little if anything that could have been done to save the six miners—drilling ultimately determined that the tunnel where the men were presumed trapped had only a half-foot of air space left.