MODEL RELEASED. Air analysis. Scientist with a gas cylinder containing a pressurised sample of air. The air will be analysed by gas chromatography to determine the levels of different gases within it. Gas chromatography separates gases due to their differing mobility through certain mediums. Gases which are particularly studied include those which trap heat in the atmosphere (greenhouse gases), & those that destroy ozone, a gas which blocks the harmful ultraviolet rays in sunlight. Photographed at the Global Atmospheric Sampling Laboratory (GASLAB) in Melbourne, Australia. GASLAB analyses air collected by ground stations, ships, & air- craft, and air extracted from ice from Antarctica.