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Dry air at 20 °C and 1 atm has a thermal diffusivity of 21.35 mm²/s (0.8273 ft²/h). This page is for dry air.
Thermal diffusivity says how fast a temperature change spreads through a material:
α = k / (ρ·cp)
It is thermal conductivity divided by volumetric heat capacity. Air has a high α for a fluid because its density is low. Use it in transient conduction (Fourier number) and in the Prandtl number, Pr = ν/α. The inputs are on the thermal conductivity, density and specific heat pages.
Because ρ is proportional to pressure, α at 10 bar is about ten times lower than at 1 atm. Compare with water thermal diffusivity.
Accuracy. Lemmon et al. (2000) state an uncertainty of about 0.1 % in density, 0.2 % in speed of sound and 1 % in heat capacity from the solidification point to 873 K (600 °C) and up to 70 MPa. Above 873 K there were no reliable air data, so nitrogen data were used and the paper gives about 0.5 % for density. Lemmon & Jacobsen (2004) state about 5 % for the viscosity and thermal conductivity of air, and more near the critical point. Viscosity and conductivity above about 600 °C, and the 1000 °C end of the range, are less certain than that. CoolProp uses a molar mass of 28.96546 g/mol, the U.S. Standard Atmosphere uses 28.9644 g/mol. That is the main reason CoolProp density at 15 °C and 1 atm is 0.04 % above the Standard Atmosphere value. α combines three properties, so its uncertainty is roughly 5 % or more.