Source: http://en.wikipedia.org/wiki/Viscosity

Viscosity of selected gases at 100 kPa, (μPa·s)
Gasat 0 °C (273 K)at 27 °C (300 K)
air 17.4 18.6
hydrogen 8.4 9.0
helium   20.0
argon   22.9
xenon 21.2 23.2
carbon dioxide   15.0
methane   11.2
ethane   9.5