| Nike Air, the sneakers with cushioning support never relied
on air for their "airbags". Instead sulfur
hexafluoride gas (SF6) was used. Sulfur hexafluoride is a stable,
dense gas (6.602 g/L; about five times denser than air).
Nike is currently phasing out the use of sulfur
hexafluoride in their Nike Air cushions, because it is a serious
greenhouse gas. In 2000, Nike used 200 000 lb of sulfur
hexafluoride for their sneakers. The newer gas cushions will be filled
with nitrogen.
Time to swap the old Nike SF6 sneakers for a green pair of Nike
Nitrogen? | 
