Argon in nonflammable, heavier than air and undergoes practically no chemical reactions. Most industrially produced argon is used as shielding gas for welding and in metallurgy – in the production of steel, pure silicon or titanium, for example. It is used as a solvent in automatic fire extinguisher systems and, in a mixture with helium, ensures that airbags inflate instantaneously in an emergency. Its low thermal conductivity makes the noble gas a good choice as a filling gas for the interstitial space in double glazed windows. It is also used in winemaking for transfer pumping and as gas filling in barrels to protect wine from oxidation. Argon is also used as filling gas for light bulbs and as lighting gas for gas discharge lamps. In the latter, it produces the typical violet color.