Dry Air

Gases & Other

Density: 0.001205 g/cm³

Dry air at standard temperature and pressure (20°C, 1 atm). Used for streaming calculations, room modeling, and atmospheric transport.

Composition

Nuclide / Element	Fraction
Nitrogen	0.755300
Oxygen	0.231800
Argon	0.012900

Code output

MCNP

c Dry Air (STP)
c Density: 0.001205 g/cm3 (use -0.001205 on cell card)
c Weight fractions
m38    7014.80c -0.7553  $ N
       8016.80c -0.2318  $ O
      18000.80c -0.0129  $ Ar

Notes

Density at 20°C, 1 atm. Ar-41 activation (from Ar-40 neutron capture) is a radiological concern near reactor containment.

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