Helium is nearly 7 times better at conducting heat than both air and nitrogen [0], lower density [1] and about the same viscosity [2]. [0] http://www.engineeri

Helium is nearly 7 times better at conducting heat than both air and nitrogen [0], lower density [1] and about the same viscosity [2]. [0] http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html http://www.engineeringtoolbox.com/thermal-conductivity-d_429... [1] http://www.engineeringtoolbox.com/gas-density-d_158.html http://www.engineeringtoolbox.com/gas-density-d_158.html [2] http://hyperphysics.phy-astr.gsu.edu/hbase/tables/viscosity.html http://hyperphysics.phy-astr.gsu.edu/hbase/tables/viscosity....